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  • 701.
    Svenungsson, Josefine
    University West, Department of Engineering Science, Division of Welding Technology.
    Keyhole laser process for welding Titanium alloy: modelling and experiment2016Conference paper (Other academic)
  • 702.
    Tamil Alagan, Nageswaran
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Enhanced heat transfer and tool wear in high-pressure coolant assisted turning of alloy 7182019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heat generated in a machining process is a common and critical obstacle faced in today's manufacturing industries. The heat generated in the cutting zone has adirect negative influence on the tool life, which, in turn contributes to increasing the manufacturing costs. Especially in the machining of Heat Resistant Superalloys, HRSA, this is a very limiting factor. HRSA are capable of retaining their mechanical strength and hardness at elevated temperatures. This property is advantageous for applications such as aero-engines, but also a disadvantage, since it also lowers the machinability significantly.This work is an attempt to improve the heat transfer from the cutting zone, which would lead to an increase in the tool life. To achieve this goal, the effect of cooling the flank face (tertiary shear zone) with high-pressure is studied; furthermore, the cutting tool has been modified to create an improved interface between the high pressure coolant and the tool where high-temperature gradient exists.Three main generations of inserts have been designed and investigated. Firstly, an insert with surface texture features created with the purpose of increasing the available surface area for heat dissipation: First generation, Gen I. Secondly, GenI+, a modified rake design of Gen I, for improved frictional conditions on the tool-chip contact. Thirdly, Gen II was designed as a further improvement of GenI. Here, several channel features on the rake face were added, reaching out from the contact zone to the near proximity of the cutting edge. This has the purpose of improving access of the coolant closer to the cutting edge.The experiments were conducted in facing operations of Alloy 718 with uncoated round carbide inserts. All experiments were carried out with high-pressure coolant, with a maximum available pressure of 16 MPa on the rake face and 8MPa on the flank face, respectively. The three generations of inserts, Gen I, I+and II, were experimentally evaluated by tool wear analysis in comparison with a regular insert. The results shows that the tool life increased significantly for the Gen I insert, compared to catastrophic failure of the regular insert at the same conditions. Regarding the Gen II insert, an increase in tool life by approximately30-40 percent, compared to Gen I inserts was observed. XRegarding the coolant-boiling phenomenon, results revealed the existence in form of dark region (Ca precipitate) below the flank wear land. The location and size of the coolant-boiling region is interrelated between flank wear, cutting zone temperature, coolant pressure and vapour pressure of the coolant at the investigated coolant pressure levels. The coolant applied at a pressure lower than the vapour pressure of the coolant itself will cause the "Leidenfrost effect" to appear that will effectively act as a coolant barrier region. However, most importantly, this effect led to the observation of a new wear mechanism present "Cavitation Wear". This type of wear appears in the form of erosion pits on the flank surface of the insert and it is observed for flank pressure conditions of 4and 8 MPa. It is a new phenomenon in tool wear to be seen on uncoated WC cutting tools during machining operations with high-pressure coolant.

  • 703.
    Tamil Alagan, Nageswaran
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Textured insert for improved heat extraction in combination with high-pressure cooling in turning of superalloys2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heat generated in a machining process is a common and critical obstacle faced in today's machining industries. The heat generated in the cutting zone has a direct negative influence on the tool life which, in turn contributes to increase the manufacturing costs. Especially, in machining of Heat Resistant Super Alloys, HRSA this is a very limiting factor. HRSA are capable of retaining their mechanical strength and hardness at elevated temperatures. This property is advantageous in the application in e.g. aero-engines but also a disadvantage, since it also lowers the machinability significantly. This work is an attempt to improve the heat transfer from the cutting zone, which would lead to an increase in the tool life. To achieve this goal, the cutting tool has been modified to create an improved interface between the coolant and tool in the high-temperature areas. Two generations of inserts have been designed and investigated. Firstly, an insert with surface texture features has been created with the purpose of increasing the available surface area for heat dissipation: First generation, Gen I. Secondly, a GenII was designed as a further improvement of Gen I. Here, several channel features on the rake face were added, reaching out from the contact zone to the near proximity of the cutting edge. This with the purpose of improving access of the coolant closer to the cutting edge. The experiments were conducted in facing operations of Alloy 718 with uncoated round carbide inserts. All experiments were carried out with high-pressure coolant assistance, with a pressure of 16 MPa on the rake face and 8 MPa on the flankface, respectively.The two generations of inserts, Gen I and Gen II, were experimentally evaluated by tool wear analysis in comparison with a regular insert. The results shows that the tool life increased significantly for the Gen I insert, compared to a catastrophic failure of the regular insert at the same conditions. Regarding the Gen II insert,an increase in tool life by approximately 30 to 40 percent compared to Gen I insert was observed.

  • 704.
    Tamil Alagan, Nageswaran
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hoier, Philipp
    Chalmers University of Technology, Department of Industrial and Materials Science, SE-412 96 Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, SE-412 96 Gothenburg, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, SE-461 81 Trollhättan, Sweden.
    Influence of Surface Features for Increased Heat Dissipation on Tool Wear2018In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, no 5, article id E664Article in journal (Refereed)
    Abstract [en]

    The critical problems faced during the machining process of heat resistant superalloys, (HRSA), is the concentration of heat in the cutting zone and the difficulty in dissipating it. The concentrated heat in the cutting zone has a negative influence on the tool life and surface quality of the machined surface, which in turn, contributes to higher manufacturing costs. This paper investigates improved heat dissipation from the cutting zone on the tool wear through surface features on the cutting tools. Firstly, the objective was to increase the available surface area in high temperature regions of the cutting tool. Secondly, multiple surface features were fabricated for the purpose of acting as channels in the rake face to create better access for the coolant to the proximity of the cutting edge. The purpose was thereby to improve the cooling of the cutting edge itself, which exhibits the highest temperature during machining. These modified inserts were experimentally investigated in face turning of Alloy 718 with high-pressure coolant. Overall results exhibited that surface featured inserts decreased flank wear, abrasion of the flank face, cutting edge deterioration and crater wear probably due to better heat dissipation from the cutting zone.

  • 705.
    Tamil Alagan, Nageswaran
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, 461 81, Sweden.
    Investigation of Modified Cutting Insert with Forced Coolant Application in Machining of Alloy 7182016In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 42, p. 481-486Article in journal (Refereed)
    Abstract [en]

    Abstract In the last decades machining methods have witnessed an advancement in both cutting tools and coolant/lubrication, sometimes in combination with high pressure jet. The aim of this work is to investigate a modified cutting insert with forced coolant application, FCA, how it influences the tool-chip contact in the secondary shear zone and how it affects the tool wear when turning Alloy 718. During the machining process the main and frequent problems are heat generation and friction in the cutting zone, which has a direct impact on the cutting tool life. High pressure jet cooling have headwayed the cutting technology for the last five decades, showing an improvment of tool life, reduced temperature in the cutting zone and better surface integrity of the workpiece. These developments have practically enhanced the capability and quality in machining of superalloys. This paper is an advancement of the previous work, increasing surface area of the insert, with a additional channel design to improve the coolant reachability in the tool-chip contact area on the rake face. The influence in tool wear has been investigated. Through a set of experiments, a channel design insert with forced coolant application, has shown about 24-33% decrease in tool wear compared to only a textured insert. Hybrid inserts with its cooling and channel features have even widened the operational cutting region with significantly less tool wear.

  • 706.
    Tamil Alagan, Nageswaran
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Next Generation Insert for Forced Coolant Application in Machining of Inconel 7182016In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 836-837, p. 340-347Article in journal (Refereed)
    Abstract [en]

    Machining technology has undergone an extensive evolution throughout the last decades in its capability to machine hard-to-cut material. This paper will discuss about the next generation insert with cooling feature coupled with forced coolant in machining Inconel 718. The geometry of the insert was changed in a way which has enlarged the surface area approximately 12% compared to regular insert named as nusselt insert. The idea applied in “nusselt insert” was the relation of increase in surface area to heat dissipation. Forced coolant application has become a way to improve existing metal cutting concepts and improve their current material removal rates without any need for a reengineered machining process. Experiments conducted on the inserts is that the first experiment of its kind in machining technology together with forced coolant and tested in four different inserts. The primary focus of the work was the investigation of the relation between the heat dissipation with an increase in surface area/mass ratio in the cutting interface based on its influence on tool wear. The experimental results showed the nusselt insert have better ability for heat dissipation which has led to significant reduce in tool wear and successfully facing Inconel 718 at vc 105 m/min, f 0.3 mm/rev and ap 1 mm where the regular insert had a catastrophic failure at vc 90 m/min, f 0.1 mm/rev and ap 1 mm. Nusselt insert has shown to increase MRR significantly compared to regular insert.

  • 707.
    Tamil Alagan, Nageswaran
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hoier, Philipp
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Zeman, Pavel
    Department of Production Machines and Equipment, Faculty of Mechanica lEngineering, Center of Advanced AerospaceTechnology, CzechTechnical University in Prague, Czech Republic.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Swede.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB,Trollhättan, Sweden.
    Effects of high pressure cooling in the flank and rake faces of WC tool on the tool wear mechanism and process conditions in turning of alloy 7182019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 434-435, article id 102922Article in journal (Refereed)
    Abstract [en]

    The exceptional properties of Heat Resistant Super Alloys (HRSA) justify the search for advanced technologiesthat can improve the capability of machining these materials. One such advanced technology is the applicationof a coolant at high pressure while machining, a strategic solution known for at least six decades. The aim is toachieve extended tool life, better chip control and improved surface finish. Another aim is to control the temperature in the workpiece/tool interface targeting for optimum cutting conditions. In most of the existing applications with high-pressure coolant media, the nozzles are positioned on the rake face side of the insert andthey are directed towards the cutting edge (the high-temperature area). The coolant is applied at high-pressureto improve the penetration of the cooling media along the cutting edge in the interface between the insert andworkpiece material (chip) as well as to increase chip breakability. However, the corresponding infusion ofcoolant media in the interface between the flank face of the insert and the work material (tertiary shear zone) hasbeen previously only scarcely addressed, as is the combined effect of coolant applications on rake and clearancesides of the insert. The present work addresses the influence of different pressure conditions in (flank: 0, 4 and8 MPa; rake: 8 and 16 MPa) on maximum flank wear, flank wear area, tool wear mechanism, and overall processperformance. Round uncoated inserts are used in a set of face turning experiments, conducted on the widely usedHRSA "Alloy 718" and run in two condition tests with respect to cutting speed (45 (low) and 90 (high) m/min).The results show that an increase in rake pressure from 8 to 16 MPa has certainly a positive impact on tool life.Furthermore, at higher vc of 90 m/min, cutting edge deterioration: due to an extensive abrasion and crack in thewear zone were the dominant wear mechanism. Nevertheless, the increase in coolant pressure condition to16 MPa reduced the amount of abrasion on the tool compared to 8 MPa. At the lower cutting speed, no crack orplastic deformation or extensive abrasion were found. When using 8 MPa pressure of coolant media on the flank,the wear was reduced by 20% compared to flood cooling conditions. Application of high-pressure cooling on theflank face has a positive effect on tool life and overall machining performance of Alloy 718.

  • 708.
    Tamil Alagan, Nageswaran
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zeman, Pavel
    Czech Technical University in Prague, Research Center of Manufacturing Technology, Prague, Czech Republic.
    Hoier, Philipp
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Investigation of micro-textured cutting tools used for face turning of alloy 718 with high-pressure cooling2019In: Journal of manufacturing processes, ISSN 1526-6125, Vol. 37, p. 606-616Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand to improve the service life of cutting tools during machining of heat resistant superalloys (HRSA). Various studies showed that textured cutting tools improved the tribological properties and reduced cutting forces, temperature, and tool wear. Surface texturing can be seen as a futuristic design to improve the performance of the cutting tool and to increase productivity. However, only limited research has been conducted in machining superalloys with textured inserts and high-pressure coolant. In this work, three different micro texture designs on both rake and flank face are investigated in combination with high-pressure coolant in machining Alloy 718. Due to better tool life predictability, carbide cutting tools are used in machining components made from superalloys. However, the disadvantage is that machining can only be done at lower cutting speed/feed rate/depth of cut with high tool wear rates. The experimental investigation using different tool wear analysis methods showed that the combination of a cylindrical dimple on the rake and the square pyramid texture on the flank surface improved the wear resistance of the tool. An increase in tool life of about 30% was achieved as compared with a regular insert for the investigated cutting conditions. Different levels of adhering workpiece material were observed on the rake face of textured tools. Furthermore, the chip backside showed imprints from the tool textures. The tool textures on the rake face have influenced the tool-chip friction conditions during cutting.

  • 709.
    Tano, Ingrid
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering and Natural Sciences.
    Nylen, Per
    University West, Department of Engineering Science.
    Wigren, Jan
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Relationships between Coating Microstructure and Thermal Conductivity in Thermal Barrier Coatings – A modelling Approach2010In: International Thermal Spray Conference and Exposition, ITCS Singapore 2010: 3-5 May 2010,  Singapore, Düsseldorft: DVS Media , 2010, p. 66-72Conference paper (Refereed)
    Abstract [en]

    Fundamental understanding of relationships between coating microstructure and thermal conductivity is important to be able to understand the influence of coating defects, such as delaminations and pores, on heat insulation in thermal barrier coatings. Object-Oriented Finite element analysis (OOF) has recently been shown as an effective tool for evaluating thermo-mechanical material behaviour, because of this method's capability to incorporate the inherent material microstructure as an input to the model. In this work, this method was combined with multi-variate statistical modelling. The statistical model was used for screening and tentative relationship building and the finite element model was thereafter used for verification of the statistical modelling results. Characterisation of the coatings included microstructure, porosity and crack content and thermal conductivity measurements. A range of coating architectures was investigated including High purity Yttria stabilised Zirconia, Dysprosia stabilised Zirconia and Dysprosia stabilised Zirconia with porosity former. Evaluation of the thermal conductivity was conducted using the Laser Flash Technique. The microstructures were examined both on as-sprayed samples as well as on heat treated samples. The feasibility of the combined two modelling approaches, including their capability to establish relationships between coating microstructure and thermal conductivity, is discussed.

  • 710.
    Tano, Ingrid
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Vännman, Kerstin
    Umeå universitet & Luleå tekniska universitet.
    Multivariate process capability analysis applied on a thermal spraying process2011In: 25th International Conference on Surface Modification Technologies, SMT25, University West in Trollhättan, Sweden, on June 20-22, 2011., 2011Conference paper (Refereed)
    Abstract [en]

    Abstract

    Our interest in multivariate capability indices (MPCI) is based on a case from a thermal spray­ing process at Volvo Aero Corporation, Sweden, where they wanted to determine the process capability of a three-dimensional variable. The process can be characterized as a high temperature “spray paint­ing” to protect the sprayed surface against, e.g. heat, corrosion and erosion. Different porosity is desirable depending on what the thermally sprayed coating should protect against. There is a relation be­tween the porosity and the in-flame variables and it would be preferable to se­cure the porosity during spraying instead as of today, afterwards. Since the three-dimensional, in-flame, variables are correlated one way to do this could be to calculate a MPCI of the in-flame variables. There are a number of different MPCIs described in the literature, but for only a hand­ful of these confidence intervals have been derived. In practise the conclusion about process capability must be drawn from a random sample. Hence, confidence or tests for MPCIs are important. Four different available methods for calcu­lating confidence intervals of MPCIs are being reviewed and compared. Current investigation shows issues that need to be solved before the studied methods can be applied more generally in practice.

  • 711.
    Teixeira, Felipe Ribeiro
    et al.
    Federal University of Pará, Department of Mechanical Engineering/PPGEM, 1 Augusto Corrêa St., Guamá, Belém, PA, 66075-110, Brazil.
    Mota, Carlos Alberto Mendes
    Federal University of Pará, Department of Mechanical Engineering/PPGEM, 1 Augusto Corrêa St., Guamá, Belém, PA, 66075-110, Brazil.
    Almeida, Hélio Antônio Lameira
    Federal Institute of Education, Science and Technology of Pará, Mechanics, 1155 Alm. Barroso Ave., Marco, Belém, PA, 66093-020, Brazil.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Welding Technology. Federal University of Uberlandia, Laprosolda (Center for Research and Development of Welding Processes), 2121 João Naves de Ávila Ave., Santa Mônica, Uberlandia, MG, 38400-902, Brazil.
    Operational behavior of the switchback GMAW process using a mechanized rig for arc movement2019In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 269, p. 135-149Article in journal (Refereed)
    Abstract [en]

    Switchback Gas Metal Arc Welding (GMAW) consists of a forward and backward periodic oscillation of the welding torch in the longitudinal direction of the joint. The present work has two objectives, to evaluate the use of a simple and practical device proposed for the switchback manipulation of the torch and to analyze the effect of the switchback parameters on the operational characteristic of the process. Two series of bead-on-plate depositions were planned, using the GMAW process with or without the switchback technique. To find an operational envelope, two levels of equivalent welding speeds were used for covering ranges of oscillation frequency and amplitude. A Ni superalloy was employed as deposition material, aiming at simulating weld overlays. Wire feeding speed, set voltage and contact tip-to-work distance (CTWD) were kept constant. The proposed device was evaluated and proved to be able to make the overlays with all combinations of planned parameters. It was demonstrated that if the backward length (B) is larger than half of the forward's (F), the torch passes more often over the same point of the deposit, and the oftener the torch passes over the same point, the lower the incidence of intermittent narrowing of the bead. By evaluating the surface aspect of the beads, the greater the F, the higher the likelihood of this irregularity. Penetration is shallower with switchback (reason demonstrated based on the fraction of stroke length that the arc is over the subtract), yet the bead surface presents more ripples. Another incident non-geometric conformity is the "dragon back" aspect of the bead, which is favored by faster equivalent welding speeds and high values of forward and backward speeds. The found operational envelope for the GMAW process with switchback was stablished with low-values of speeds and lengths of forward and backward strokes.

  • 712.
    Tesar, Tomas
    et al.
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic; Czech Technical University in Prague, Faculty of Nuclear Science and Physical Engineering, Department of Materials, Trojanova 13, 120 00 Praha 2, Czech Republic .
    Musalek, Radek
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Lukac, Frantisek
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Cizek, Jan
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Rimal, Vaclav
    Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Praha 8, Czech Republic.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Chraska, Tomas
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Increasing α-phase content of alumina-chromia coatings deposited by suspension plasma spraying using hybrid and intermixed concepts2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no S1, p. 298-311Article in journal (Refereed)
    Abstract [en]

    The novel method of hybrid suspension plasma spraying of dry coarse aluminum oxide powder with chromium oxide suspension using hybrid water/argon-stabilized (WSP-H 500) plasma torch was utilized for the deposition of coatings with very high α-phase content reaching up to 90%. The deposition mechanism and phase composition were compared with those of coatings deposited from i) intermixed alumina-chromia suspension and ii) alumina suspension doped with chromium nitrate nonahydrate solution. All deposition routes showed alternative ways of preparation of novel multimaterial coatings. It was demonstrated that the chromia addition and the deposition route play the crucial role in the pronounced formation of the thermodynamically stable α-phase. © 2019

  • 713.
    Thalavai Pandian, Karthikeyan
    University West, Department of Engineering Science, Division of Welding Technology.
    Introduction of high-quality welds in production: Benefits and challenges2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The main objective of this work is to evaluate the different post weld improvement methods like burr grinding, TIG treatment and HFMI from a production standpoint (repeatability, productivity, and cost) and determine the best suitable method for production scenario. The work summarizes the benefits and challenges with different post weld improvement method and provides the guideline/recommendation to follow for each method. Process variation is known to be one of the major concerns in accurately predicting the fatigue life of the welded structures. In order to reduce the process variation, a study has been conducted to determine the key parameters (like toe radius, flank angle and undercut) that have more significant influence on the fatigue life. The study helps to understand the right amount of effort required to generate the optimum output so that non-value added work could be potentially avoided. This will result in faster processing time which in turn increases the productivity. In this thesis work, the fatigue properties are evaluated at a load level (R=-1), which is similar to the actual load level for construction equipment. Most of the samples are tested at the same stress level to know the benefits in using a high strength material along with the improvement technique. The fatigue load cycle includes an initial peak load to understand the relaxation of beneficial compressive residual stresses when subjected to actual service loads, particularly in HFMI method. In such relaxation scenario, the geometry benefits become more significant and an improved geometry profile for HFMI treatment is also discussed. The thesis result shows Burr Grinding method is much preferred from production standpoint and it has a life improvement of about 3x to 8x times as compared to design life goals. Further work is needed to determine the effectiveness of the method in removing defects and the possibility to take the benefits of crack initiation life. Also, more testing is needed at different stress levels to determine the slope of the proposed method which may help to further optimize the design demands.

  • 714.
    Thomas, C.A.
    et al.
    ESS. Lund, Sweden.
    Hartl, M.A.
    ESS. Lund, Sweden.
    Lee, Y
    ESS. Lund, Sweden.
    Shea, T.J
    ESS. Lund, Sweden.
    Adli, E.
    University of Oslo, Oslo, Norway.
    Gjersdal, H.
    University of Oslo, Oslo, Norway.
    Jaekel, M.R.
    University of Oslo, Oslo, Norway.
    Rohne, O.
    University of Oslo, Oslo, Norway.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Preliminary Measurement On Potential Luminescent Coating Material For The Ess Target Imaging Systems: Transverse Profile Monitors2017In: Proceedings of IBIC2016, Barcelona, Spain, 2017, p. 559-562Conference paper (Other academic)
  • 715.
    Tofeldt, Oskar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Pierce, S.G.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Smillie, G.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Kerr, W.
    Advanced Forming Research Centre, Inchinnan, Renfrewshire, UK.
    Flockhart, G.M.H.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Macleod, C.N.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Blue, R.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Gachagan, A.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Stratoudaki, T.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    McMahon, D.
    Advanced Forming Research Centre, Inchinnan, Renfrewshire, UK.
    Investigation of fundamental ultrasonic propagation characteristics in NDT of Electron Beam Melted additive manufactured samples: Inconel 7182018Conference paper (Other academic)
    Abstract [en]

    New approaches for efficient NDT inspection of modern additively manufactured metallic components are required urgently to qualify and validate the next generation of metallic parts across a range of industries. Ultrasonic testing is a fundamental component of NDT for such additive manufacturing processes. This work studies the ultrasonic propagation characteristics of EBM manufactured sample coupons in Inconel 718material. Fundamental longitudinal and shear wave velocity measurements are experimentally measured in 3 orthogonal build directions of the sample coupons. Results show a dependency of the ultrasonic velocities and the build direction. The measured velocities are further verified in a phased array measurement showing successful results that highlights the potential of continued studies with synthetic apertures techniques.

  • 716.
    Tofeldt, Oskar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ryden, Nils
    Lund University, Sweden .
    Guided wave evaluation techniques for testing of plate-like concrete structures2018Conference paper (Other academic)
    Abstract [en]

    There is a growing need for non-destructive techniques capable of investigating civilengineering structures of concrete material. The Impact-Echo (IE) method is one suchtechnique based on the study of a resonant and stationary mode. This mode corresponds to a Lamb mode. In turn, this accentuates that the IE method can easily be extended to include the analysis of propagating Lamb modes as well. Thereby a quantitative evaluation of the elastic plate properties and thickness is possible. Moreover, the use of Lamb waves lay the foundations for extended analysis which makes measurements based on an extension of the IE method an attractive complement to current ultrasonic techniques for plate-like concrete structures.

  • 717.
    Tolvanen, Sakari
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Welding Technology. Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron2018In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 5, p. 1683-1691Article in journal (Refereed)
    Abstract [en]

    Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an improved alloy to be widely applicable for large aerospace structural components, successful welding of such castings is essential. In the present work, the microstructure and porosity of laser welds in a standard grade cast Ti-6Al-4V alloy as well as two modified alloy versions with different boron concentrations have been investigated. Prior-β grain reconstruction revealed the prior-β grain structure in the weld zones. In fusion zones of the welds, boron was found to refine the grain size significantly and rendered narrow elongated grains. TiB particles in the prior-β grain boundaries in the cast base material restricted grain growth in the heat-affected zone. The TiB particles that existed in the as cast alloys decreased in size in the fusion zones of welds. The hardness in the weld zones was higher than in the base material and boron did not have a significant effect on hardness of the weld zones. The fusion zones were smaller in the boron-modified alloys as compared with Ti-6Al-4V without boron. Computed tomography X-ray investigations of the laser welds showed that pores in the FZ of the boron modified alloys were confined to the lower part of the welds, suggesting that boron addition influences melt pool flow. © 2018 The Author(s)

  • 718.
    Tricarico, L.
    et al.
    DMMM – Politecnico di Bari, viale Japigia 182, Bari, Italy.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. CNR-IFN UOS Bari, via Amendola 173, 70126 Bari, Italy.
    Palumbo, G.
    DMMM – Politecnico di Bari, viale Japigia 182, Bari, Italy.
    Sorgente, D.
    CNR-IFN UOS Bari, via Amendola 173, Bari, Italy.
    Spina, R.
    DMMM – Politecnico di Bari, viale Japigia 182, Bari, Italy.
    Lugarà, P.M.
    CNR-IFN UOS Bari, via Amendola 173, Bari, Italy.
    Discrete spot laser hardening and remelting with a high-brilliance source for surface structuring of a hypereutectoid steel2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 115, p. 194-202Article in journal (Refereed)
    Abstract [en]

    In this work the single-pulse laser irradiation of a hypereutectoid steel was investigated using a fiber laser source, in a range of process parameters enabling surface hardening and remelting. Effects of laser power, pulse energy and defocusing distance were investigated using a numerical/experimental approach. Laser surface treatments were conducted on uncoated samples without any gas shielding, changing both the laser power and the pulse energy, and exploring a wide range of defocusing distances. Numerical simulations were conducted using a finite element model calibrated by means of an optimization procedure based on a specific calculation algorithm and using a subset of experimental data producing surface melting. Using both simulations and experiments, the process operating windows of the discrete spot laser treatment were determined: it was found that, when varying the laser power between 250 W and 750 W, melt-free hardened zones are produced with a maximum extension between 0.7 mm and 1.0 mm; on the contrary, in case of more tightly beam focusing conditions, surface melting occurred with a size of the re-melted areas ranging between 1.0 mm and 1.4 mm. Results further showed that a small change (generally 2–3 mm) of the defocusing distance suddenly brings the material from melting to a non-hardening condition. © 2016 Elsevier Ltd

  • 719.
    Tricarico, Luigi
    et al.
    DMMM, Politecnico di Bari, Viale Japigia 182, Bari, 70126, Italy; CNR-IFN UOS Bari, Via Amendola 173, Bari, 70126, Italy.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. CNR-IFN UOS Bari, Via Amendola 173, Bari, 70126, Italy.
    Palumbo, Gianfranco
    DMMM, Politecnico di Bari, Viale Japigia 182, Bari, 70126, Italy; CNR-IFN UOS Bari, Via Amendola 173, Bari, 70126, Italy.
    Sorgente, Donato
    NR-IFN UOS Bari, Via Amendola 173, Bari, 70126, Italy; Università degli Studi della Basilicata, School of Engineering, Via Ateneo Lucano, 10, Potenza, 85100, Italy .
    Corizzo, Ottavio
    DMMM, Politecnico di Bari, Viale Japigia 182, Bari, 70126, Italy.
    Spina, Roberto
    DMMM, Politecnico di Bari, Viale Japigia 182, Bari, 70126, Italy; CNR-IFN UOS Bari, Via Amendola 173, Bari, 70126, Italy.
    Lugara, Pietro Mario
    CNR-IFN UOS Bari, Via Amendola 173, Bari, 70126, Italy; Università degli Studi e Politecnico di Bari, Dipartimento di Fisica, Via Amendola 173, Bari, 70126, Italy .
    Numerical and experimental investigation of the discrete spot laser hardening of a graphite-coated hypereutectoid steel using a fibre laser2019In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 104, no 1-4, p. 1393-1402Article in journal (Refereed)
    Abstract [en]

    The single-pulse laser hardening of a hypereutectoid steel coated by a graphite layer was investigated using a numerical/experimental approach. Experimental tests were conducted on coated samples using a fibre laser source and without any gas shielding aiming to explore the effect of laser power, pulse energy and defocusing distance on the dimensions of the hardened region. The process operating window of the discrete spot laser hardening using the graphite layer was determined through a finite element model and compared with previous results obtained on uncoated samples. For the same laser power and interaction times, an enlargement of the hardened region was found when using the graphite coating, especially when operating at the lowest laser energy level. The process operating window remains similar in shape to the one of the uncoated steel but moves towards larger hardened diameters and much larger defocusing distances. Once the maximum temperature has been fixed, a linear relationship between the hardened diameter and the defocusing distance exists. No obvious surface oxidation occurs since the graphite coating acts as a protective layer. © 2019, Springer-Verlag London Ltd., part of Springer Nature.

  • 720.
    Tu, Juei-feng
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. North Carolina State University, Department of Mechanical & Aerospace Engineering, Raleigh, United States.
    Rajule, Nilesh
    North Carolina State University, Department of Mechanical & Aerospace Engineering, Raleigh, United States.
    Liu, Yi
    North Carolina State University, Raleigh, Department of Material Science and Engineering,United States.
    Martin, James
    North Carolina State University, Department of Chemistry, Raleigh, United State.
    Nanostructure diffraction analysis of a copper/single walled carbon nanotube nanocomposite synthesized by Laser Surface Implanting2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 113, p. 1-9Article in journal (Refereed)
    Abstract [en]

    A new wet process, denoted as Laser Surface Implanting (LSI), has been developed to synthesize a Copper-Single Wall Carbon NanoTube (Cu-SWCNT) metal nanocomposite by dispersing SWCNTs into molten copper, followed by rapid and non-equilibrium solidification to form the Cu-SWCNT nanocomposite such that dispersed SWCNTs could locked in positions without agglomerating into large clusters. However, the nanometer sizes of the SWCNT clusters inside this nanocomposite make it extremely difficult to obtain TEM images with discernable SWCNT clusters in the copper matrix. In this paper, TEM images and their diffraction patterns for annealed pure copper, quenched pure copper (by the same synthesis process without introducing SWCNTs), and Cu-SWCNT nanocomposite are compared. It is concluded that TEM images with discernable SWCNT clusters are rare. Therefore, diffraction patterns are better tools to identify SWCNTs within the copper matrix. The indexed diffraction patterns confirm that the copper fcc lattice is preserved. However, the Cu-SWCNT nanocomposite samples also exhibit ordered diffuse scattering, consisting of at least two polyhedra of diffuse-scattering bounded by the 110* and 200* family of reciprocal lattice planes, respectively. In addition several samples exhibit super-lattice Bragg diffraction indicative expanded unit cells. It thus appears that the SWCNTs are incorporated into the Cu matrix with precise arrangements commensurate with specific Cu lattice planes. 

  • 721.
    Tu, Juei-feng
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. North Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA.
    Rajule, Nilesh
    North Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA.
    Molian, Pal
    Iowa State Univ, Dept Mech Engn, Ames, IA USA.
    Liu, Yi
    Fiat Chrysler Automobiles, Auburn Hills, MI USA.
    Laser synthesis of a copper-single-walled carbon nanotube nanocomposite via molecular-level mixing and non-equilibrium solidification2016In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 49, article id 495301Article in journal (Refereed)
    Abstract [en]

    A copper-single-walled carbon nanotube (Cu-SWCNT) metal nanocomposite could be an ideal material if it can substantially improve the strength of copper while preserving the metal’s excellent thermal and electrical properties. However, synthesis of such a nanocomposite is highly challenging, because copper and SWCNTs do not form intermetallic compounds and are insoluble; as a result, there are serious issues regarding wettability and fine dispersion of SWCNTs within the copper matrix. In this paper we present a novel wet process, called the laser surface implantation process (LSI), to synthesize Cu-SWCNT nanocomposites by mixing SWCNTs into molten copper. The LSI process includes drilling several microholes on a copper substrate, filling the microholes with SWCNTs suspended in solution, and melting the copper substrate to create a micro-well of molten copper. The molten copper advances radially outward to engulf the microholes with pre-deposited SWCNTs to form the Cu-SWCNT implant upon solidification. Rapid and non-equilibrium solidification is achieved due to copper’s excellent heat conductivity, so that SWCNTs are locked in position within the copper matrix without agglomerating into large clusters. This wet process is very different from the typical dry processes used in powder metallurgy. Very high hardness improvement, up to 527% over pure copper, was achieved, confirmed by micro-indentation tests, with only a 0.23% SWCNT volume fraction. The nanostructure of the nanocomposite was characterized by TEM imaging, energy-dispersive x-ray spectroscopy mapping and spectroscopy measurements. The SWCNTs were found to be finely dispersed within the copper matrix with cluster sizes in the range of nanometers, achieving the goal of molecular-level mixing.

  • 722.
    Valiente Bermejo, María Asunción
    University West, Department of Engineering Science, Division of Welding Technology.
    Teaching Welding with a Flipped Classroom Approach2019In: Welding Journal, ISSN 0043-2296, Vol. 98, no 9, p. 42-45Article in journal (Refereed)
  • 723.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    DebRoy, Tarasankar
    University Park, Department of Materials Science and Engineering, The Pennsylvania State University, State College PA 16801, USA.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Towards a Map of Solidification Cracking Risk in Laser Welding of Austenitic Stainless Steels2015In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 78, p. 230-239Article in journal (Refereed)
    Abstract [en]

    In this work, two series of specimens with Hammar and Svensson's Cr- and Ni-equivalents (Creq+Nieq) = 35 and 45 wt% were used to cover a wide range of austenitic grades. These were laser welded with different energy inputs achieving cooling rates in the range of 103 °C/s to 104 °C/s. As high cooling rates and rapid solidification conditions could favour fully austenitic solidification and therefore raise susceptibility to solidification cracking, the solidification modes of the laser welded specimens were compared to the ones experienced by the same alloys under arc welding conditions. It was found that high cooling rates experienced in laser welding promoted fully austenitic solidification for a wider range of compositions, for example specimens with (Creq+Nieq) = 35% under arc welding cooling conditions at 10 °C/s showed fully austenitic solidification up to Creq/Nieq = 1.30, whilst the same specimens laser cooled at 103 °C/s showed fully austenitic solidification up to Creq/Nieq = 1.50 and those cooled at 104 °C/s showed it up to Creq/Nieq = 1.68. Therefore, high cooling rates extended the solidification cracking risk to a wider range of Creq/Nieq values. This work also compares the cooling rates experimentally determined by thermocouples to the computed cooling rates calculated by a highly-advanced computational model. The distance between the thermocouple's wires and the thermal resistance of thermocouples together with the small size of the weld pools proved to be practical limitations in the experimental determination of cooling rates. However, an excellent agreement was found between computed and experimental solidus isotherms at high energy input settings. For low energy input settings cooling rate was in the order of magnitude of 104 °C/s, whilst for high energy input settings cooling rate was found to be in the order of magnitude of 103 °C/s.

  • 724.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Eyzop, Daniel
    Outokumpu Stainless AB, Avesta R&D Center, 774 41 Avesta, Sweden.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel2019In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 6, article id 1050Article in journal (Refereed)
    Abstract [en]

    Type 2507 superduplex stainless steel 20 mm in thickness was multi-pass-welded with Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW) processes. Recommended and higher arc energies and inter-pass temperatures were used. Thermal cycles were monitored using a recently developed procedure involving the successive instrumentation of the multi-pass welds, pass by pass, by addition of thermocouples in each weld pass. The repeatability of temperature measurements and survival rate of more than 90% of thermocouples confirmed the reliability of the procedure. Reheating by subsequent passes caused a progressive increase in the austenite content of the weld metal. The as-deposited GMAW passes with higher-than-recommended arc energy showed the lowest presence of nitrides. Therefore, the cooling rate—and not the time exposed at the critical temperature range—seems to be the key factor for nitride formation. The welding sequence layout also plays an important role in the distribution of secondary phases. A larger amount and concentration of secondary austenite and σ-phase was found for a larger number of subsequent passes in the immediate vicinity of a specific weld pass. The impact toughness exceeded requirements for all welds. Differences in absorbed energies were related to the amount of micro-inclusions found with the FCAW weld showing the lowest absorbed energies and highest amount of micro-inclusions. Pitting corrosion preferentially initiated in locations with secondary austenite and σ-phase. However, in the absence of these secondary phases, the HAZ containing nitrides was the weakest location where pitting initiated. The results of this work have implications on practical welding for superduplex stainless steels: the current recommendations on maximum arc energy should be revised for large thickness weldments, and the importance of the welding sequence layout on the formation of secondary phases should be considered.

  • 725.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Hosseini, Vahid
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Monitoring Thermal Cycles in Multi-pass Welding2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Swedish Production Academy , 2016, p. 1-5Conference paper (Refereed)
    Abstract [sv]

    Differently from any previous investigation in welding, this research work presents a novel development that allows temperature to be measured and recorded simultaneously with up to 32 thermocouples indifferent locations of a welding joint. Four experiments were designed to optimise the measurement technique by comparing the performance of three types of thermocouples (K, N, C) insulated with different materials and varying the insertion technique of the thermocouples in the joint. Results showed that type-K thermocouple had the best performance and proved that glass fibre insulation provided better protection than Inconel. The optimised measurement procedure developed in this work enables to monitor the thermal cycles in multi-pass welds. That information is essential in multi-pass welding of materials such as super duplex stainless steels, carbon steels or nickel alloys, as heating them repeatedly makes them susceptible to the formation of brittle phases and in turn it influences their mechanical and corrosion properties. This technique could be really important for future applications such as temperature modellingor prediction of mechanical properties and microstructure in relation to the thermal cycle experienced by alloys susceptible to the formation of undesirable phases.

  • 726.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    DebRoy, Tarasankar
    Pennsylvania State University.
    Influence of low energy laser welding on solidification and microstructure of austenitic stainless steel welds2013In: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan, Hans Engström, Luleå: Luleå University of Technology, 2013, p. 3-14Conference paper (Refereed)
    Abstract [en]

    Primary austenitic solidification is related to increased hot cracking susceptibility in welding of austenitic stainless steels. It is also recognised that high cooling rates and rapid solidification conditions, like those achieved in laser beam welding (LBW), increase the stability of austenite versus ferrite as the primary solidification phase. Knowledge about the solidification mode under LBW conditions is therefore of utmost importance. A series of austenitic stainless steel alloys were prepared using an electric arc furnace and cooled at a rate of 10 ºC/s. The overall alloying composition was kept constant at [Cr eq+Nieq] = 40 wt% while changing the Cr eq/Nieq ratio from 1.52 to 1.84. These alloys were then laser welded using a continuous wave ytterbium fibre laser at two different energy input levels. Cooling rates were experimentally determined to be in the range of 10 3 ºC/s to 104 ºC/s and the values were confirmed by computational modelling. The compositional border between primary austenitic and primary ferritic solidification was found to shift to higher Cr eq/Nieq values at higher cooling rates. However, all the alloys showed coexistence of regions of primary austenitic and primary ferritic solidification for both laser settings although ustenite tended to more abundant at higher cooling rates. Austenite content and refinement of microstructure is discussed in terms of effects of cooling rate on solidification behaviour and solid state transformations.

  • 727.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Optimising Quality and Productivity in Welding of Duplex and Superduplex Stainless Steels2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-7Conference paper (Refereed)
    Abstract [en]

    The aim of this work was to study the influence of shielding gases and welding positions on properties of duplex and superduplex stainless steel circumferential pipe welds. Corrosion resistance, microstructural features and weld defects were assessed and related to the welding procedures. Horizontal and vertical upward welding positions produced high quality welds. However, welding in the overhead position resulted in less good results in terms of porosity and corrosion resistance. Shielding gases containing 30% helium showed best results, whilst using a mixture Ar+2%CO2 resulted in undercuts and porosity in all welding positions.

  • 728.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Hurtig, Kjell
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Rasmuson, H.
    ESAB AB, Göteborg, Sweden.
    Frodigh, M.
    Sandvik Materials Technology, Sandviken, Sweden.
    Bengtsson, P.
    AGA Gas AB, Lidingö, Sweden.
    Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds2015In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, no 2, p. 239-249Article in journal (Refereed)
    Abstract [en]

    The influence of shielding gases on welding performanceand on properties of duplex and superduplex stainlesssteel welds was studied. Using argon as the reference gas,helium, nitrogen and carbon dioxide were added and fivemixtures evaluated. Bead-on-plate welds and circumferentialpipe welds were produced using mechanisedGMAwelding inthe downhand position. Welding performance, corrosion resistance,mechanical properties, microstructural features andweld imperfections were assessed and related to the shieldinggas. Shielding gases containing 30 % helium showed excellentresults; whilst pure argon showed unstable arc and poorweld pool fluidity and Ar+2 %CO2 resulted in underfill andporosity. Mixtures containing helium resulted in higher ductilitywelds and higher impact toughness values than weldsproduced with Ar+2 %CO2. Sound and balanced duplexmicrostructures free from intermetallics were found with suitableferrite contents for all the shielding gases studied. All theduplex pipe welds passed the corrosion test regardless of theshielding gas used, and the best results in the corrosion test forsuperduplex pipe welds were found when using Ar+30 %He+0.5 %CO2+1.8 %N2 as shielding gas.

  • 729.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Rasmuson, H.
    ESAB AB, Goteborg Svezia, Sweden.
    Frodigh, M.
    Sandvik Materials Technology, Sandviken, Svezia, Sweden.
    Bengtsson, P.
    AG A Gas AB, Germany .
    Influenza del gas di protezione sul comportamento e le proprietà  di giunti sa dati di acciai duplex e superduplex: Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds2016In: Rivista Italiana della Saldatura, ISSN 0035-6794, Vol. 68, no 5, p. 635-650Article in journal (Other academic)
    Abstract [en]

    The influence of shielding gases on welding performance and on properties of duplex and superduplex stainless steel welds was studied. Using argon as the reference gas, helium, nitrogen and carbon dioxide were added and five mixtures evaluated. Bead-on-plate welds and circumferential pipe welds were produced using mechanised GMA welding in the downhand position. Welding performance, corrosion resistance, mechanical properties, microstructural features and weld imperfections were assessed and related to the shielding gas. Shielding gases containing 30% helium showed excellent results; whilst pure argon showed unstable arc and poor weld pool fluidity and Ar + 2% CO2resulted in underfill and porosity. Mixtures containing helium resulted in higher ductility welds and higher impact toughness values than welds produced with Ar + 2% CO2. Sound and balanced duplex microstructures free from intermetallics were found with suitable ferrite contents for all the shielding gases studied. All the duplex pipe welds passed the corrosion test regardless of the shielding gas used, and the best results in the corrosion test for superduplex pipe welds were found when using Ar + 30%He + 0.5% CO2+ 1.8% N2as shielding gas.

  • 730.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Rasmuson, Helene
    ESAB AB, Göteborg, Sweden.
    Frodigh, Mette
    Sandvik Materials Technology, Sandviken, Sweden .
    Bengtsson, Per
    AGA Gas AB, Lidingö, Sweden.
    Effect of welding position on properties of duplex and superduplex stainless steel circumferential welds2015In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, no 5, p. 693-703Article in journal (Refereed)
    Abstract [en]

    The influence of welding position on properties ofduplex and superduplex stainless steel welds was studied. Circumferential pipe welds were produced using mechanised gasmetal arc welding in flat position, vertical up position and overhead position. Dilution, corrosion resistance, mechanical properties, microstructural features and weld imperfections were assessed and related to the welding position. Welds produced in flat and vertical up positions were less likely to produce porosity than those welded in overhead position, whilst underfill was not observed in overhead position welds. All the duplex pipe welds passed the corrosion test regardless of the welding position and showed sound microstructures. Under fixed arc energy conditions, welds produced in vertical up position showed the lowest dilution values whilst welds in flat position showed the highest. Excellent impact toughness values and cross tensile values were found regardless of the welding positions. Whenever possible, flat position is recommended as welds showed less proneness to porosity. Vertical up position is recommended as the second best choice.

  • 731.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Wessman, Sten
    Swerim AB, Kista, Sweden.
    Computational thermodynamics in ferrite content prediction of austenitic stainless steel weldments2019In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 3, p. 627-635Article in journal (Refereed)
    Abstract [en]

    In this paper, four computational approaches using Thermo-Calc and DICTRA have been used to calculate the ferrite content of a set of austenitic stainless steel welds with different solidification modes and ferrite contents. To evaluate the computational approaches, the calculations were compared to the experimental results. It was found that for each solidification mode, there is one computational approach that predicts ferrite with better accuracy. For ferritic-austenitic alloys, the best accuracy is obtained when considering the peritectic model, with deviations of 1.2–1.4% ferrite. In the case of austenitic-ferritic alloys, the solidification analysed through the eutectic approach showed an accuracy of 0.6–1.6% ferrite, whilst in alloys with fully ferritic solidification, starting calculations, not from the liquid state but from fully ferritic below solidus, was the best approach, showing 2.3% ferrite deviation from the experimental measurements. Computational thermodynamics has proved to be a promising tool to explore simulation and calculation of ferrite content phase fractions in welding. However, further investigation is still needed to correlate the real microstructural features with the computational parameter “cell size”. The feasibility and accuracy of computational thermodynamics when predicting ferrite in low-heat-input welding processes such as laser welding is also another aspect for additional investigation.

  • 732.
    Valiente Bermejo, María Asunción
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Zhang, Zhuyao
    Metrode Products Limited, Hanworth Lane, Chertsey, Surrey.
    Relevance and limitations of arc furnace casting in welding research2015In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 28, no 2, p. 97-104Article in journal (Refereed)
    Abstract [en]

    The arc furnace melting technique is widely used for positive material identification in the industry of welding consumable manufacturing. It is also a convenient method for sample preparations ofvarious pre-design chemical compositions for investigations on solidification, phase transformationand microstructure of different alloys. However, up to now, welding research works using the arc furnace melting technique did not report to follow any international standard. This is the first time that an international standard involving arc furnace casting is discussed and evaluated to be applied in the welding research field. In this paper, the specimens obtained with the ASTM E1306-94 standard are assessed, and some suggestions are proposed for modification and improvement of the standard, like adding some intermediate steps including the turning over ofthe specimen and an extra melting. By adopting those proposals in the procedure, cast samples with complete melting and chemical composition homogeneity were achieved.

  • 733.
    Valleti, Krishna
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur P.O., Hyderabad, India.
    Krishna, D. Murali
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur P.O., Hyderabad, India.
    Reddy, P. Mohan
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur P.O., Hyderabad, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West. International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur P.O., Hyderabad, India.
    High temperature stable solar selective coatings by cathodic arc PVD for heat collecting elements2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 145, no 3, p. 447-453Article in journal (Refereed)
    Abstract [en]

    A functionally multilayered Cr/CrTiAlN-G/TiAlN/AlSiN/AlSiO coating configuration, suitable for enhancing solar selectivity of stainless steel substrates used in concentrated solar power (CSP) systems, has been formulated using cathodic arc physical vapor deposition (CAPVD) technique. The sequence of functional layers was decided based on their refractive index values and their relative thickness was optimized to achieve maximum solar selectivity. The optimized coating exhibits encouraging values of solar absorptivity (α) – 0.95 and thermal emissivity (ε) – 0.09 to 0.14 up to 600 °C. Further, the solar selectivity factor (α/ε) for the coating is found to be comparable with the best selective coatings currently available for elevated temperature operation. The coatings were also studied for their long term stability and found to be stable up to 500 °C, although considerable change in optical properties was observed on increasing the temperature to 600 °C. The noted properties make the present coating a promising candidate as a high temperature solar selective coating on stainless steel substrates.

  • 734.
    Valleti, Krishna
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Puneet, C.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Rama Krishna, L.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Studies on cathodic arc PVD grown TiCrN based erosion resistant thin films2016In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 34, no 4, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Titanium chromium nitride (TiCrN) coatings with varying Cr content in two configurations, mono- and multilayer, were deposited on high speed steel substrates using a cylindrical cathodic arc physical vapor deposition technique. The physical, mechanical, and erosion behavior of the coatings were investigated. Among the monolayer coatings, the thicker Ti0.48Cr0.52N coatings yielded the best erosion resistance property. But with the increase in thickness, a considerable increase in residual stress is observed. Toward minimizing the stress accumulation, the effect of multilayering with periodic in situ heat treatment (after each 1 μm film growth) was studied by growing films in Ti0.52Cr0.48N/Ti0.40Cr0.60N bilayer configuration. A new approach based on % area of erosion damage for measuring relative wear rate of thin films has been proposed and implemented. The multilayer coatings exhibited superior erosion performance compared to the well-known erosion resistant TiN coatings that are in use for compressor blades from past few decades. Further, the erosion failure mechanisms in TiCrN coatings were also studied and found to be clearly different for mono- and multilayer configurations. The results reveal that the thicker multilayer TiCrN coatings (20 μm) exhibit promising choice for erosion resistance applications.

  • 735.
    Vardelle, Armelle
    et al.
    University of Limoges, Limoges, France..
    Moreau, Christian
    Concordia University, Montreal, Canada..
    Akedo, Jun
    National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan..
    Ashrafizadeh, Hossein
    University of Alberta, Edmonton, Canada..
    Berndt, Christopher C.
    Swinburne University of Technology, Hawthorn, Australia..
    Berghaus, Jörg Oberste
    Swinburne University of Technology, Hawthorn, Australia..
    Boulos, Maher
    University of Sherbrooke, Sherbrooke, Canada..
    Brogan, Jeffrey
    Mesoscribe Technologies, Inc., St. James, USA..
    Bourtsalas, Athanasios C.
    Columbia University, New York, USA..
    Dolatabadi, Ali
    Concordia University, Montreal, Canada..
    Dorfman, Mitchell
    Oerlikon Metco, Inc., Westbury, USA.
    Eden, Timothy J.
    The Pennsylvania State University, State College, USA..
    Fauchais, Pierre
    University of Limoges, Limoges, France..
    Fisher, Gary
    Alberta Innovates - Technology Futures, Edmonton, Canada..
    Gaertner, Frank
    Helmut Schmidt University, Hamburg, Germany..
    Gindrat, Malko
    Oerlikon Metco AG,Wohlen, Switzerland..
    Henne, Rudolf
    German Aerospace Center (DLR), Stuttgart, Germany..
    Hyland, Margaret
    University of Auckland, Auckland, New Zealand..
    Irissou, Eric
    National Research Council of Canada, Boucherville, Canada..
    Jodoin, Bertrand
    University of Ottawa, Department of Mechanical Engineering, Ottawa, Canada.
    Jordan, Eric H.
    University of Connecticut, Storrs, USA..
    Khor, Khiam Aik
    Nanyang Technological University, Singapore, Singapore..
    Killinger, Andreas
    Universität Stuttgart, Stuttgart, Germany..
    Lau, Yuk-Chiu
    GE Power, Niskayuna, USA..
    Li, Chang-Jiu
    Xi’an Jiaotong University, Xi’an, China..
    Li, Li
    Praxair Surface Technologies, Inc.,Indianapolis, USA..
    Longtin, Jon
    Stony Brook University, Stony Brook, USA..
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Masset, Patrick J.
    Fraunhofer UMSICHT, Sulzbach-Rosenberg, Germany..
    Matejicek, Jiri
    Institute of Plasma Physics, Prague, Czech Republic..
    Mauer, Georg
    Forschungszentrum Jülich Institute of Energy and Climate Research, Jülich, Germany.
    McDonald, André
    University of Alberta, Edmonton, Canada..
    Mostaghimi, Javad
    University of Toronto,Toronto, Canada..
    Sampath, Sanjay
    Stony Brook University, Stony Brook, USA..
    Schiller, Günter
    German Aerospace Center (DLR), Stuttgart, Germany..
    Shinoda, Kentaro
    National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan..
    Smith, Mark F.
    Sandia National Laboratories, Albuquerque, USA..
    Syed, Asif Ansar
    German Aerospace Center (DLR), Stuttgart, Germany..
    Themelis, Nickolas J.
    Columbia University, New York, USA..
    Toma, Filofteia-Laura
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany..
    Trelles, Juan Pablo
    University of Massachusetts Lowell, Lowell, USA..
    Vassen, Robert
    Forschungszentrum Jülich Institute of Energy and Climate Research, Jülich, Germany..
    Vuoristo, Petri
    Tampere University of Technology,Tampere, Finland..
    Erratum to The 2016 Thermal Spray Roadmap2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 5, p. 985-986Article in journal (Refereed)
  • 736.
    Vardelle, Armelle
    et al.
    University of Limoges, Limoges, France.
    Moreau, Christian
    Concordia University, Montreal, Canada.
    Akedo, Jun
    National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
    Ashrafizadeh, Hossein
    University of Alberta, Edmonton, Canada.
    Berndt, Christopher C.
    Swinburne University of Technology, Hawthorn, Australia.
    Berghaus, Jörg Oberste
    Swinburne University of Technology,Hawthorn, Australia.
    Boulos, Maher
    University of Sherbrooke, Sherbrooke, Canada.
    Brogan, Jeffrey
    Mesoscribe Technologies, Inc., St. James, USA.
    Bourtsalas, Athanasios C.
    Columbia University, New York, USA.
    Dolatabadi, Ali
    Concordia University, Montreal, Canada.
    Dorfman, Mitchell
    Oerlikon Metco, Inc., Westbury, USA.
    Eden, Timothy J.
    The Pennsylvania State University, State College, USA.
    Fauchais, Pierre
    University of Limoges, Limoges, France.
    Fisher, Gary
    Alberta Innovates - Technology Futures, Edmonton, Canada.
    Gaertner, Frank
    Helmut Schmidt University, Hamburg, Germany.
    Gindrat, Malko
    Oerlikon Metco AG,Wohlen, Switzerland.
    Henne, Rudolf
    German Aerospace Center (DLR), Stuttgart, Germany.
    Hyland, Margret
    University of Auckland, Auckland, New Zealand.
    Irissou, Eric
    National Research Council of Canada, Boucherville, Canada.
    Jodain, Bertrand
    University of Ottawa, Department of Mechanical Engineering, Ottawa, Canada.
    Jordan, Eric H.
    University of Connecticut, Storrs, USA.
    Khor, Khiam Aik
    Nanyang Technological University, Singapore, Singapore.
    Killinger, Andreas
    Universität Stuttgart, Stuttgart, Germany.
    Lau, Yuk-Chiu
    GE Power, Niskayuna, USA.
    Li, Chang-Jiu
    Xi’an Jiaotong University, Xi’an, China.
    Li, Li
    Praxair Surface Technologies, Inc.,Indianapolis, USA.
    Longtin, Jon
    Stony Brook University, Stony Brook, USA.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Masset, Patrick J.
    Fraunhofer UMSICHT, Sulzbach-Rosenberg, Germany.
    Matejicek, Jiri
    Institute of Plasma Physics, Prague, Czech Republic.
    Mauer, Georg
    Forschungszentrum Jülich Institute of Energy and Climate Research, Jülich, Germany.
    McDonald, André
    University of Alberta, Edmonton, Canada.
    Mostaghimi, Javad
    University of Toronto,Toronto, Canada.
    Sampath, Sanjay
    Stony Brook University, Stony Brook, USA.
    Schiller, Günter
    German Aerospace Center (DLR), Stuttgart, Germany.
    Shinoda, Kentaro
    National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
    Smith, Mark F.
    Sandia National Laboratories, Albuquerque, USA.
    Syed, Asif Ansar
    German Aerospace Center (DLR), Stuttgart, Germany.
    Themelis, Nickolas J.
    Columbia University, New York, USA.
    Toma, Filofteia-Laura
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Trelles, Juan Pablo
    University of Massachusetts Lowell, Lowell, USA.
    Vassen, Robert
    Forschungszentrum Jülich Institute of Energy and Climate Research, Jülich, Germany.
    Vuoristo, Petri
    Tampere University of Technology,Tampere, Finland.
    The 2016 Thermal Spray Roadmap2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 8, p. 1376-1440Article in journal (Refereed)
    Abstract [en]

    Considerable progress has been made over the last decades in thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new problems and market requirements. This article aims to identify the current challenges limiting the evolution of these technologies and to propose research directions and priorities to meet these challenges. It was prepared on the basis of a collection of short articles written by experts in thermal spray who were asked to present a snapshot of the current state of their specific field, give their views on current challenges faced by the field and provide some guidance as to the R&D required to meet these challenges. The article is divided in three sections that deal with the emerging thermal spray processes, coating properties and function, and biomedical, electronic, aerospace and energy generation applications. © 2016, ASM International.

  • 737. Vassen, Robert
    et al.
    Cernuschi, Federico
    Rizzi, Gabriele
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Östergren, Lars
    Kloosterman, Arien
    Mevrel, Remy
    Feist, Jorg
    Nicholls, John
    Overview in the field of thermal barrier coatings including burner rig testing in the European Union2008In: Ceramics Japan, ISSN 0009-031X, Vol. 43, no 5, p. 371-382Article in journal (Other academic)
  • 738.
    Vassen, Robert
    et al.
    IEF-1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
    Cernuschi, Federico
    CESI RICERCA, Power Generation Systems Dep. Milano, Italy.
    Rizzi, Gabriele
    Turbocoating.
    Scrivani, Andrea
    Turbocoating.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Östergren, Lars
    Surface Technology, Volvo Aero Corporation, Trollhättan, Sweden.
    Kloosterman, Arjen
    National Aerospace Laboratory NLR, Gas Turbines & Structural Integrity Department, Amsterdam, The Netherlands.
    Meverel, Remy
    ONERA, Chatillon Cedex, France.
    Feist, Jörg
    Southside Thermal Sciences (STS) Ltd, London, United Kingdom.
    Nicholls, John
    Cranfield University, Cranfield, United Kingdom.
    Recent activities in the field of thermal barrier coatings including burner rig testing in the european union.2008In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 10, no 10, p. 907-921Article, review/survey (Other academic)
  • 739.
    Vassen, Robert
    et al.
    Institute of Energy Research, Jülich, Germany.
    Nylen, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Stöver, Detlev
    Institute of Energy Research, Jülich, Germany.
    Editorial2009In: Journal of Thermal Spray Technology, Vol. 18, no 2, p. 131-Article in journal (Other academic)
  • 740.
    Venkatesh, L.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India. .
    Pitchuka, Suresh Babu
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Sivakumar, G.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Gundakaram, Ravi C.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Samajdar, I.
    Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076, India.
    Microstructural response of various chromium carbide based coatings to erosion and nano impact testing2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 386-387, p. 72-79Article in journal (Refereed)
    Abstract [en]

    In this study, we demonstrate the microstructure dependency of erosion behaviour of laser clad, detonation sprayed and atmospheric plasma sprayed chromium carbide based coatings. The final chromium carbide content in all the coatings was a strong function of rapid solidification rate associated with the processes. In the laser clad coating majority of the chromium carbides re-solidified while in the thermally sprayed coatings chromium carbide re-solidification was hindered to a large extent. Hence, the final chromium carbide content in the thermally sprayed coating decreased with increased extent of particle melting during spraying. Decarburisation and oxidation during thermal spraying lead to the formation of chromium carbides with lower carbon content and chromium oxide(s). Laser clad and detonation sprayed coatings, with higher chromium carbide content, showed lower erosion rates and exhibited fewer brittle erosion events. Embrittlement due to excessive dissolution of chromium carbides into the matrix and poor splat bonding were found to be the reasons for higher erosion rate of the plasma sprayed coating. Scanning electron microscopy and quantification of single erodent impact events clearly established ductile material removal in the laser clad and detonation sprayed coating and brittle material removal in the plasma sprayed coating as the dominant mechanism(s). A good agreement was found between solid particle erosion testing and nano impact testing results.

  • 741.
    Venkatesh, Lakshmi Narayanan
    et al.
    Int Adv Res Ctr Powder Met & New Mat ARCI, Hyderabad 500005, Andhra Pradesh, India.
    Babu, Pitchuka Suresh
    Int Adv Res Ctr Powder Met & New Mat ARCI, Hyderabad 500005, Andhra Pradesh, India.
    Gundakaram, Ravi Chandra
    Int Adv Res Ctr Powder Met & New Mat ARCI, Hyderabad 500005, Andhra Pradesh, India.
    Doherty, Roger D.
    Drexel Univ, Dept Mat Engn, Philadelphia, PA 19104 USA.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Samajdar, Indradev
    Indian Inst Technol, Dept Met Engn & Mat Sci, Mumbai 400076, Maharashtra, India.
    Morphology-Dependent Hardness of Cr7C3-Ni-Rich Alloy Composite vs Orientation Independent Hardness of Cr7C3 Primary Phase in a Laser Clad Microstructure2017In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, no 4, p. 1534-1539Article in journal (Refereed)
    Abstract [en]

    Microstructural evolution with superheating was studied in chromium carbide-nickel coatings deposited by laser cladding. At lower superheating, selective growth of aOE (c) 0001 > direction from the high density of Cr7C3 grains nucleated resulted in a columnar structure with (0001) texture. Increased superheating lead to the loss of columnar structure as well as the (0001) texture. The hexagonal Cr7C3 showed an unusual isotropic nanoindentation hardness evidently correlated with its low c/a ratio. However, the rod-like morphology of the carbide dendrites resulted in significant anisotropy in the hardness of the composite.

  • 742.
    Venkatesh, Lakshmi Narayanan
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India; Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076, India.
    Venkataraman, B.
    Defence Metallurgical Research Laboratory (DMRL), Kanchanbagh, Hyderabad 500058, India.
    Tak, Manish
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Sivakumar, Ganapathy S.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Gundakaram, Ravi C.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Samajdar, Indradev S.
    Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076, India.
    Room temperature and 600 °C erosion behaviour of various chromium carbide composite coatings2019In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 422-423, p. 44-53Article in journal (Refereed)
    Abstract [en]

    In this study, the erosion behaviour of laser clad chromium carbide-Ni rich alloy composite coatings with a wide range of carbide contents at room temperature and 600 °C were investigated. The variation in carbide content of the coatings was due to dilution from the substrate and the high cooling rate in the laser cladding process preventing re-solidification of the molten carbides. Erosion rate was observed to be a function of carbide content alone and was significantly higher at 600 °C as compared to room temperature. Erosion wear ratio (E90/E30) was also dependent on carbide content but decreased at higher temperature and higher carbide contents. A comparison of erosion behaviour with detonation and plasma sprayed counterparts showed the superior performance of laser clad coatings at 600 °C. The poor erosion performance of the detonation and plasma sprayed coatings was due to weak splat bonding. Thick oxide layer formed on the steel substrate after pre-oxidation resulted in its poor erosion performance.

  • 743.
    Vijay, S.
    et al.
    BITS Pilani, Pilani, India.
    Roy, B.
    BITS Pilani, Pilani, India.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wetting properties of ceramic reinforced metal matrix composites on varied roughness profiles2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc. , 2017, Vol. 1, p. 537-542Conference paper (Refereed)
    Abstract [en]

    Superhydrophobic surfaces are of great importance in many industrial applications, especially where components are exposed to wet environments and low temperatures.Texturing of surfaces to reach superhydrophobicity can be achieved by thermal spraying technology, which is an attractive coating method as it is cheap, flexible and can employ a large range of feedstock materials. In this study, ceramic reinforced metal matrix composite (WC-CoCr) powders were sprayed using High Velocity Air Fuel method. They were varied based on their powder parameters such as carbide grain size, binder grain size and powder strength. The purpose was to investigate their hydrophobic characteristics and how these are influenced by different roughness profiles. The wetting properties such as contact angle and contact angle hysteresis were first investigated for the as-sprayed coatings. The roughness properties and Hausdorff Dimension were then related to the wetting properties. Aside from as-sprayed coatings, the effect of roughness and inherent wetting characteristics were studied by investigating the coating surface after grit blasting and polishing. Results show that powder parameters can lead to designing surfaces with higher surface roughnesses and thus having higher contact angles. It was also shown that surface composition of cermets has an impact on wettability, with the binder accounting for wetting characteristics and carbides accounting for roughness. 

  • 744.
    Vijay, Sudarshan
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Roy, B.
    Investigation of wetting properties of ceramic reinforced metal matrixc omposites on varied roughness profiles2017Conference paper (Other academic)
  • 745.
    Vijay, Sudarshan
    et al.
    Birla Institute of Technology and Science-Pilani (BITS-Pilani), Pilani, India.
    Wang, Litian
    Østfold University College, Fredrikstad, Norway.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Surface characteristics investigation of HVAF sprayed cermet coatings2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 493, p. 956-962Article in journal (Refereed)
    Abstract [en]

    Superhydrophobic surfaces that are durable and can be easily manufactured are of high interest for many industrial applications. Measuring and understanding roughness in the context of superhydrophobicity is the first step in creation of a surface that does not require activation to be hydrophobic. In this study, the as sprayed surface of different cermet (WC-10Co4Cr and Cr3C2-25Ni20Cr) coatings produced by High Velocity Air Fuel (HVAF) spraying – have been investigated to assess their wetting ability. In order to address the challenges raised by the specific roughness profile of thermal spray surfaces, two routes have been adapted and used for surface characteristics analysis i.e. statistical and fractal. Results show that both methods have a strong correlation to wettability. Roughness parameters Sdq and Sdr show good correlation with advancing contact angle. Hausdorff Dimension of a sub-micrometer profile shows good relation with the contact angle and provides information for state of the droplet. To determine how to increase the contact angle of the coating surface, coating parameters such as CGS Density have been correlated with Hausdorff Dimension. Both methods provide good understanding in terms of wettability of rough cermet surfaces. © 2019 Elsevier B.V.

  • 746.
    Volpe, Annalisa
    et al.
    CNR-IFN, Institute for Photonics and Nanotechnologies, S.S. Bari, via Amendola 173, Bari, Italy.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. CNR-IFN, Institute for Photonics and Nanotechnologies, S.S. Bari, via Amendola 173, Bari, Italy.
    Trotta, Gianluca
    CNR-ITIA, Institute of Industrial Technology and Automation, Bari, Italy.
    Vázquez, Rebeca Martinez
    CNR-IFN, Institute for Photonics and Nanotechnologies, Milan, Italy.
    Fassi, Irene
    CNR-ITIA, Institute of Industrial Technology and Automation, Milan, Italy.
    Osellame, Roberto
    CNR-IFN, Institute for Photonics and Nanotechnologies, Milan, Italy.
    Fabrication and assembling of a microfluidic optical stretcher polymeric chip combining femtosecond laser and micro injection molding technologies2017In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 10092, article id 100920FArticle in journal (Refereed)
    Abstract [en]

    Microfluidic optical stretchers are valuable optofluidic devices for studying single cell mechanical properties. These usually consist of a single microfluidic channel where cells, with dimensions ranging from 5 to 20 Όm are trapped and manipulated through optical forces induced by two counter-propagating laser beams. Recently, monolithic optical stretchers have been directly fabricated in fused silica by femtosecond laser micromachining (FLM). Such a technology allows writing in a single step in the substrate volume both the microfluidic channel and the optical waveguides with a high degree of precision and flexibility. However, this method is very slow and cannot be applied to cheaper materials like polymers. Therefore, novel technological platforms are needed to boost the production of such devices on a mass scale. In this work, we propose integration of FLM with micro-injection moulding (ΌIM) as a novel route towards the cost-effective and flexible manufacturing of polymeric Lab-on-a-Chip (LOC) devices. In particular, we have fabricated and assembled a polymethylmethacrylate (PMMA) microfluidic optical stretcher by exploiting firstly FLM to manufacture a metallic mould prototype with reconfigurable inserts. Afterwards, such mould was employed for the production, through ΌIM, of the two PMMA thin plates composing the device. The microchannel with reservoirs and lodgings for the optical fibers delivering the laser radiation for cell trapping were reproduced on one plate, while the other included access holes to the channel. The device was assembled by direct fs-laser welding, ensuring sealing of the channel and avoiding thermal deformation and/or contamination. © 2017 SPIE.

  • 747.
    Vouristo, P.
    et al.
    Tempere University of Technology, Tampere, Finland.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Industrial and research activities in thermal spray technology in the Nordic region of Europe2009In: Expanding Thermal Spray Performance to New Markets and Applications - 2009 International Thermal Spray Conference, ITSC 2009: 4-7 May, Las Vegas, 2009, p. 517-522Conference paper (Other academic)
    Abstract [en]

    Thermal spraying is used widely in many industrial sectors in the North European Countries: Finland, Sweden, Norway and Denmark. Important areas where thermal spraying is used petroleum, paper, metals, transport, defence and high-tech machinery industries. In Finland thermal spray technology has wideest use in the pulp and paper industries with several companies spraying various types of rolls and cylinders. In Sweden, thermal spray technology is of great importance in the manufacture of aero engines and in industrial gas turbine applications. In Norway thermal spraying is widely used in various offshore applications, including subsea oil drilling enterprises. Development and innovation in thermal spray technology in the Nordic countries is dominated by research conducted in Finland and Sweden, followed by Denmark and Norway. In particular, research groups from Sweden and Finland, as well as from Norway, have routinely presented their research results at international conferences and in international journals.

  • 748.
    Vuoristo, Petri
    et al.
    Tampere University of Technology.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Industrial and research activities in thermal spray technology in the Nordic region of Europe2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 466-471Article in journal (Refereed)
  • 749.
    Wanner, Bertil
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Production Engineering.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Pejryd, Lars
    University West, Department of Engineering Science, Division of Production Engineering.
    Milling Strategies for Thin-walled Components2012In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 498, p. 177-182Article in journal (Refereed)
    Abstract [en]

    Recent developments in the Aerospace industry have led to thin-walled, reduced-weight engine designs. Due to demands in manufacturing, production speeds and material removal rates (MRR) have increased. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter-free process. The results show the differences in force response for three geometries while varying the overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper outlines certain robust machining practices. It also analyzes the criticality of the choice of offset between tool and workpiece during milling setup as well as the effects that the entry and exit of cut have on system vibrations.

  • 750.
    Wanner, Bertil
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Production Engineering.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering.
    Pejryd, Lars
    University West, Department of Engineering Science, Division of Production Engineering.
    Process Stability Strategies in Milling of Thin-walled Inconel 7182011In: 4th Manufacturing Engineering Society International Conference / [ed] Manufacturing Engineering Society, 2011, p. 1-8-Conference paper (Refereed)
    Abstract [en]

    Trends in Aerospace development have led to thin-walled, reduced-weight engine designs. The demands in manufacturing have forced production speeds and material removal rates (MRR) to increase. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter free process. The results show the differences in force response for three geometries while varying the height overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper gives guidelines on how to accomplish robust machining practices. It also answers the following questions: How critical is the choice of offset between tool and workpiece during milling setup? And what effects do the entry and exit of cut have on system vibrations?

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