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  • 101.
    Li, Ran
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Isothermal Oxidation Study of Gd2Zr2O7/YSZ Multi-Layered Thermal Barrier Coatings2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Conventional yttria stabilized zirconia (YSZ) are widely used in the gas turbine to protect the substrate material from high temperature. But the common YSZ top coatings have limitations at higher temperature (above 1200

    ℃) due to significant phase transformation and intensified sintering effect. Among the list of pyrochlores, gadolinium zirconate offer very attractive properties like low thermal conductivity, high thermal expansion coefficient and CMAS resistance. However, a lower fracture toughness than YSZ and tendency to react with alumina (thermal grown oxide) can lead to lower lifetime. Therefore, multi-layered thermal barrier coating approach was attempted and compared with single layer system. Single layer (YSZ) was processed by suspension plasma spraying (SPS). Double layer coating system comprising of YSZ as the bottom ceramic layer and gadolinium zir-conate as the top ceramic coat was processed by SPS. Also, a triple layer coating system with denser gadolinium zirconate on top of double layer system, was sprayed. Denser gado-linium zirchonate acts as the sealing layer and arrest the CMAS penetration. Isothermal oxidation performance of the sprayed coating systems including bare substrate and sub-strate with bond coat were investigated for a time period of 10hr, 50hr and 100hr at 1150℃ in air environment. Weight gain was observed in all the systems investigated. Microstruc-tural analysis was carried out using optical microscopy, SEM/EDS. Phase analysis was done using X-ray diffraction (XRD). Porosity measurement was made by water impregna-tion method. It was observed that multi-layered thermal barrier coating systems of YSZ/GZ and YSZ/GZ/GZ(dense) showed lower weight gain and TGO thickness than the single layer YSZ for all exposure time (10hr, 50hr & 100hr). The triple layer system had lower weight gain and TGO thickness compared to double layer system due to lower po-rosity content. Also, from the porosity measurement data, it could be seen that sintering effect is more dominant at 10 hr. of oxidation for all the coatings systems.

  • 102. Lindgren, L-E.
    et al.
    Lundbäck, A.
    Fisk, M.
    Pedersen, R.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Industrial application of computational welding mechanics2015Conference paper (Refereed)
  • 103.
    Lindström, Per
    University West, Department of Engineering Science, Division of Manufacturing Processes. DNV Materials Technology, Det Norske Veritas AS, Høvik, Norway.
    DNV Platform of Computational Welding Mechanics2013Conference paper (Refereed)
    Abstract [en]

    This document presents the DNV Platform of Computational Welding Mechanics, CWM, with its associated CWM-methodology. That has been developed, validated and implemented as a part of DNV’s Technology Leadership program in the field of Structural Integrity and Materials Technology.A successful CWM implementation requires that the actual organisation has gained the knowledge and understanding of the following related topics:

    - Welding Engineering with an emphasis on the welding process and its thermodynamics

    - Weld process quality control such as calibration, validation as well as DAQ, (Data Acquisition)

    - Transient thermo-mechanical coupled FE-analyses and constitutive modelling

    - Computational platforms comprising the selection of hardware, operative system and FEM-code as well as suitable pre- and post-processing tools

    From that perspective there is a lack of reliable and/or hands-on oriented CWM Engineering Handbooks and best recommended practices available on the market. For that sake is the DNV CWM-methodology and its hands on solutions presented.

    The CWM-methodology described can not only be used for residual stress assessments, as presented in this report. It can also be used for various applications such as assessment of used and/or proposed WPS, Welding Procedure Specifications as well as optimisation of the manufacturing and production process of integrated metallic structures.

    From the results of a parametric CWM-study have three (3) factors been identified to drive and/or contribute to the magnitude of the weld residual stresses in ship steel plate materials. The contributing and/or driving factors identified are the

    :- Thermal- and Mechanical Boundary Conditions during the production welding

    - Yield stress difference between the base- and the weld filler material

    - Weld heat input, Q, which affects the weld cooling time

  • 104.
    Lindström, Per
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Improved CWM platform for modelling welding procedures and their effects on structural behaviour2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    A welding procedure specification is the document describing how a weld joint should be constructed. Arc weld processes are characterized by transient thermal behavior, leading to rapid changes in material properties and dynamic interaction between weld and base material. The objective of the project is to explore how the use of an improved CWM-platform affects representative stress and strain fields in order to assess welding procedure qualification records. Forthis project, the accumulated thermal and mechanical influences from the first run to the final run are brought forward, in one and the same meshed geometrical model. Both the thermal and mechanical material model of the platform are designed to be used for modelling of the base- and weld material,promoting the simulation of the intricate combination of the thermal, elastic,and plastic strains on the plastic strain hardening and the formation of residual stress fields. The output of the simulation is mainly weld cooling times, residual stresses, and deformations. This analysis is taken further by examining how residual stresses influence crack driving force under elastic and plastic loading. In addition, the output from the simulations can be used to assess the realism of the proposed welding parameters. The main experimental welding procedure examined comes from the IIW RSDP Round Robin Phase II benchmark project, where the main aim was to benchmark residual stress simulations. This work was found to contain many applicable challenges of a CWM-analysis project.

  • 105.
    Lindström, Per
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    de Blanche, Andreas
    University West, Department of Engineering Science, Division of Computer and Electrical Engineering.
    Integration and Optimization of a 64-core HPC for FEM- and/or CFD Welding Simulations2013In: Improving Simulation Prediction by Using Advanced Material Models / [ed] Nafems Nordic, Bernau am Chiemsee: NAFEMS , 2013, p. 13-18Conference paper (Refereed)
  • 106.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Internal Diameter HVAF Spraying for Wear and Corrosion Applications2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 1-2, p. 235-243Article in journal (Refereed)
    Abstract [en]

    Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automotive and off-shore industries. Alternative methods to EHC have been widely developed in the past decade by conventional HVOF processes and more recently HVAF systems, which are processing at higher kinetic energy and more particularly at lower temperature, significantly increasing wear and corrosion resistance properties. A dedicated internal diameter HVAF system is here presented, and coatings characteristics are compared to the one obtained by standard HVAF coatings. Specially R&D designed fixtures with inside bore of 200 mm have been manufactured for this purpose, with a possibility to spray samples at increasing depth up to 400 mm while simulating closed bottom bore spraying. WC-based and Cr3C2-based powder feedstock materials have been deposited onto high-strength steel substrates. Respective coating microstructures, thermally induced stresses and corrosion resistance are discussed for further optimization of coating performances. The fact that the ID-HVAF system is utilized both for spraying and gritblasting procedures is also given a particular interest.

  • 107.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, M.
    Oerlikon Metco WOKA GmbH, Barchfeld-Immelborn, Germany.
    Runte, M
    Oerlikon Metco WOKA GmbH, Barchfeld-Immelborn, Germany.
    Reisel, G.
    Oerlikon Metco WOKA GmbH, Barchfeld-Immelborn, Germany.
    Boccaccio, P.
    University of Modena and Reggio Emilia, Modena, Italy .
    Screening Design of Supersonic Air Fuel Processing for Hard Metal Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 8, p. 1323-1332Article in journal (Refereed)
    Abstract [en]

    Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances. © 2014 ASM International.

  • 108.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Östergren, Lars
    Volvo Aero Corporation.
    Sieger, Max
    Klassen, Thomas
    Binder, Kurt
    Comparative Study on the Properties of INCONEL 718 Coatings Deposited by High Velocity Thermal Spray Methods2011In: Surface Modification Technologies XXV : Proceedings of the Twenty Fith  International Conference on Surface Modification Technologies-SMT25: Trollhättan, June 20-22, 2011, 2011, p. 51-58Conference paper (Refereed)
  • 109.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Pirling, T.
    Insitute Laue- Langevin, Grenoble.
    Manescu, A.
    Universitá Politecnica delle Marche, Ancona.
    Influence of substrate preparation on HVOF IN718 coating adhesion strength2011In: Surface Modification Technologies XXV : Proceedings of the Twenty Fith International Conference on Surface Modification Technologies - SMT25: Trolhättan June 20-22, 2011, 2011, p. 59-70Conference paper (Refereed)
  • 110.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sato, K.
    Fujimi Incoporated.
    Houdkova, S.
    University of West Bohemia.
    Smazalova, E.
    University of West Bohemia.
    Lusvarghi, L.
    University of Modena and Reggio Emilia.
    Sassatelli, P.
    University of Modena and Reggio Emilia.
    Tribological Properties of Hard Metal Coatings Sprayed by High Velocity Air Fuel Process2015In: International Thermal Spray Conference ITSC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF systems can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings, making HVAF coatings attractive both economically and environmentally over its HVOFs predecessors. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviours were evaluated via standard Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), accelerated corrosion test and electrochemical polarization test at room temperature. Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbide size for different working load applications

  • 111.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vassen, Robert
    Forschungszentrum Jülich.
    Erosion Behavior of Gadolinium Zirconate/YSZ Multi-Layered Thermal Barrier Coatings Deposited by Suspension Plasma Spray2016In: Proceedings of the International Thermal Spray Conference, 2016, p. 343-347Conference paper (Refereed)
    Abstract [en]

    Yttria stabilized zirconia (8YSZ) is the standard ceramic material for thermal barrier coating (TBC)applications. However, above 1200º C, it has limitations such as poor sintering resistance & susceptibility to CMAS(Calcium Magnesium Alumino Silicates) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperature (>1200 ºC) due to its lower thermal conductivity, good sintering resistance and CMAS infiltration resistance. Single layer 8YSZ, double layer GZ/YSZand triple layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS). Microstructuralanalysis was carried out by SEM (scanning electron microscopy). Phase analysis of as sprayed TBCs was carriedout using XRD (X ray diffraction). The as sprayed multi-layered TBCs were subjected to erosion test at room temperature and their erosion resistance was compared with single layer 8YSZ. It was observed that the erosion resistance of 8YSZ TBC was higher than GZ/YSZ multi-layered TBCs at room temperature. Among the multilayered TBCs, triple layer TBC was slightly better than double layer in terms of erosion resistance.

  • 112.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Thermal conductivity and thermal cyclic fatigue of multilayered Gd2Zr2O7/YSZ thermal barrier coatings processed by suspension plasma spray2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 283, p. 329-336Article in journal (Refereed)
    Abstract [en]

    Rare earth zirconates have lower thermal conductivity, better phase stability, improved sintering resistance and CMAS (calcium magnesium alumino silicates) infiltration resistance than yttria stabilized zirconia (YSZ) at temperatures above 1200 °C. However, their lower fracture toughness and lower coefficient of thermal expansion (CTE) compared to YSZ lead to premature coating failure. In order to overcome these drawbacks at higher temperatures, a multilayered coating approach is attempted in this study and compared with the single layer YSZ. Suspension plasma spray of single layer YSZ, single layer gadolinium zirconate (GZ) and double layer GZ/YSZ was carried out. Additionally, a triple layer coating system, with denser gadolinium zirconate on top of the GZ/YSZ system was sprayed to impart an added functionality of sealing the TBC from CMAS infiltration. Microstructural analysis was done using scanning electron microscopy and optical microscopy. Columnar microstructure with vertical cracks was observed. XRD analysis was used to identify phases formed in the as sprayed TBC samples. Porosity measurements were done using water impregnation method. Thermal diffusivity of single and multi-layered coatings was obtained by laser flash analysis and thermal conductivity of the coating systems was determined. It was found that the thermal conductivity of single layer gadolinium zirconate was lower than YSZ and that the thermal conductivity of multilayered systems were between their respective single layers. The single (YSZ), double (GZ/YSZ) and triple (GZ dense/GZ/YSZ) layer TBCs were subjected to thermal cyclic fatigue (TCF) test at 1100 °C and 1200 °C. It was observed that the single layer YSZ had lowest TCF life whereas the triple layer TBC had highest TCF life irrespective of test temperature.

  • 113.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Vassen, Robert
    Forschungszentrum Julich, Inst Energy & Climate Res IEK 1, Julich, German.
    Functional performance of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings deposited by suspension plasma spray2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 208-216Article in journal (Refereed)
    Abstract [en]

    7-8 wt% yttria stabilized zirconia (YSZ) is the standard ceramic top coat material used in gasturbines to insulate the underlying metallic substrate. However, at higher temperatures(>1200 °C), phase stability and sintering becomes an issue for YSZ. At these temperatures,YSZ is also susceptible to CMAS (calcium magnesium alumino silicates) infiltration. New ceramic materials such as pyrochlores have thus been proposed due to their excellent properties such as lower thermal conductivity and better CMAS attack resistance compared to YSZ. However, pyrochlores have inferior thermo mechanical properties compared to YSZ.Therefore, double-layered TBCs with YSZ as the intermediate layer and pyrochlore as the top ceramic layer have been proposed. In this study, double layer TBC comprising gadoliniumzirconate (GZ)/YSZ and triple layer TBC (GZdense/GZ/YSZ) comprising relatively denser GZtop layer on GZ/YSZ were deposited by suspension plasma spray. Also, single layer 8YSZ TBC was suspension plasma sprayed to compare its functional performance with the multilayered TBCs. Cross sections and top surface morphology of as sprayed TBCs were analyzed by scanning electron microscopy (SEM). XRD analysis was done to identify phases formed in the top surface of as sprayed TBCs. Porosity measurements were made using water intrusionand image analysis methods. Thermal diffusivity of the as sprayed TBCs was measured using laser flash analysis and thermal conductivity of the TBCs was calculated. The multi-layered GZ/YSZ TBCs were shown to have lower thermal conductivity than the single layer YSZ. Theas sprayed TBCs were also subjected to thermal cyclic testing at 1300 ºC. The double and triple layer TBCs had a longer thermal cyclic life compared to YSZ. The failed samples were cold mounted and analyzed by SEM.

  • 114.
    Mazidi, Aimal
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Comparison of a new, high precision, energy efficient welding method with the conventional Gas Metal Arc Welding on high carbon steel base metal2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    CMT+P welding is less susceptible to hot cracking than the MAG welding process due to use of low heat input properties. Solidification cracking was found in all weld specimens that had greater 0.39KJ/mm heat inputs. Cracking occurs because of the contraction stresses generates during cooling. Hydrogen cracking is found in HAZ with low heat input parameters, this type of cracking occurred because of very rapid cooling and therefore not enough time to allow the hydrogen to dissipate from the specimen. To eliminate this type of cracking the experiment could be repeated by adding heating during welding to control and reduce the cooling rate. Due to high carbon content in the steel and very fast cooling the microstructure of the weld is martensitic in the base metal as well as the HAZ. Microstructure in the weld and base metal is martensitic due to high carbon con-tent and rapid cooling. At low heat inputs dilution is less and therefore lower carbon content in weld pool. Better weld appearance and weld quality is achieved with CMT+P welding process than the conventional GMA welding processes because of the new wire movement technology during welding

  • 115.
    Moshkani Farahani, Erfan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Simulering av GMAW svetsprocessen med hjälp av ANSYS2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In present research, a three dimensional welding process phenomenon is simulated using a commercial finite element package ANSYS® in order to study the heat distribution and residual stress in SAE 1020 fillet joint.

    Heat distribution in different points of weldment shows that peak temperature at the nods near weld line is higher than peak temperature at nods which are located further. Also, temperature shapely increases when it subject to heat input and then falls down with a relatively lower rate after peak temperature.

    Longitudinal residual stress which is most important stress field in the specimen, in HAZ region and near the weld line is tensile with maximum values but with increase of distance from weld line the stresses decrease. Contractual resistance of material at the beginning of cooling process is a reason for generating the tensile stress.

    Transverse residual stresses perpendicular to the weld line, at the beginning and end of fillet joint is compressive due to constraints and changes to tensile in the middle of weld line. Maximum transverse residual stress will be happened at the middle and by increasing the distance the stress values approach to zero. Although, transverse residual stress values are lower than longitudinal residual stress but those should be considered as a main factor in weld deign.

    As a matter of fact, in present research maximum longitude stress (100 MPa) and transverse stress (30 MPa) satisfy AWS D1.1 weld design code requirements. According to Structural Welding Code-Steel, AWS D1.1, tension or compression parallel to axis of weld shouldn't exceed base metal tensile strength i.e 420 MPa for SAE 1020. Further, shear on effective area should be less than 0.3 of nominal tensile strength of filler material i.e 126 MPa

  • 116.
    Mráz, Lubos
    et al.
    Welding Research Institute, Industrial Institute SR, Bratislava, Slovakia .
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vrána, Miroslav
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic .
    Mikula, Pavol
    Nuclear Physics Institute AS CR, v.v.i., Řež 130, Czech Republic .
    Residual stress distribution measurement by neutron diffraction of the single pass fillet steel welds2014In: 52nd International Scientific Conference on Experimental Stress Analysis (EAN 2014): Proceedings of a meeting held 2-5 June 2014, Marianske Lazne, Czech Republic., Czech Society for Mechanics ( CSM ) , 2014Conference paper (Refereed)
    Abstract [en]

    In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds which were carried out at different welding conditions, namely, with different filler materials are presented.

  • 117.
    Musalek, Radek
    et al.
    Department of Materials Engineering, Institute of Plasma Physics AS CR, v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Fatigue Performance of TBC on Structural Steel Exposed to Cyclic Bending2014In: Proceedings of the International Thermal Spray Conference, ASM International, 2014, p. 880-885Conference paper (Refereed)
    Abstract [en]

    For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by "SF-Test" device. Testing was carried out for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and evaluation of fatigue resistance alteration due to the deposited coatings.

  • 118.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering , v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Fatigue Testing of TBC on Structural Steel by Cyclic Bending2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 1-2, p. 168-174Article in journal (Refereed)
    Abstract [en]

    For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by “SF-Test” device. Testing was carried out at each stage of the TBC preparation process, i. e., for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and complete TBC: bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and demonstrated applicability of the high-frequency resonant bending test for evaluation of fatigue resistance alteration at each stage of the TBC deposition process.

  • 119.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Kovarik, Ondrej
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Pala, Zdenek
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Hausild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Materials.
    Capek, Jiri
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Solid State Engineering.
    Kolarik, Kamil
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Solid State Engineering.
    Nicholas, Curry
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue Performance of TBCs on Hastelloy X Substrate During Cyclic Bending2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 231-243Article in journal (Refereed)
    Abstract [en]

    Our previous experiments with low-cost steel substrates confirmed that individual steps of conventional thermal barrier coating (TBC) deposition may influence fatigue properties of the coated samples differently. In the presented study, testing was carried out for TBC samples deposited on industrially more relevant Hastelloy X substrates. Samples were tested after each step of the TBC deposition process: as-received (non-coated), grit-blasted, bond-coated (NiCoCrAlY), and bond-coated + top-coated yttria-stabilized zirconia (YSZ). Conventional atmospheric plasma spraying (APS) was used for deposition of bond coat and top coat. In addition, for one half of the samples, dual-layer bond coat was prepared by combination of high-velocity air-fuel (HVAF) and APS processes. Samples were tested in the as-sprayed condition and after 100 hours annealing at 980 °C, which simulated application-relevant in-service conditions. Obtained results showed that each stage of the TBC manufacturing process as well as the simulated in-service heat exposure may significantly influence the fatigue properties of the TBC coated part. HVAF grit-blasting substantially increased the fatigue performance of the uncoated substrates. This beneficial effect was suppressed by deposition of APS bond coat but not by deposition of dual-layer HVAF + APS bond coat. All heat-treated samples showed again enhanced fatigue performance. © 2015 ASM International

  • 120.
    Musalek, Radek
    et al.
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Pala, Zdenek
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Prague, Czech Republic.
    Tomek, Libor
    Czech Technical University in Prague, Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue performance of TBCs on hastelioy X substrate during cyclic bending2015In: Thermal Spray 2015: Proceedings from the International Thermal Spray Conference (May 11–14, 2015, Long Beach, California, USA) / [ed] Agarwal A.,Lau Y.-C.,McDonald A.,Bolelli G.,Toma F.-L.,Concustell A.,Widener C.A.,Turunen, ASM International, 2015, Vol. 1, p. 406-412Conference paper (Refereed)
    Abstract [en]

    Our previous experiments with low-cost steel substrates confirmed that individual steps of conventional thermal barrier coating (TBC) deposition may influence fatigue properties of the coated samples differently. In this study, testing was carried out for TBC samples deposited on industrially more relevant Hastelioy X substrates. Samples were tested after each step of TBC deposition process: As-received (non- coated), grit-blasted, bond-coated (NiCoCrAlY) and bond- coated + top-coated (yttria-stabilized zirconia - YSZ). Conventional atmospheric plasma spraying (APS) with gas stabilized plasma torch was used for deposition of both bond coat and top coat. In addition, for one half of the samples, bond coat was prepared by consecutive combination of HVAF (High Velocity Air Fuel) and APS processes. Samples were tested both in as-sprayed condition and after 100 hours annealing at 980 °C, which simulated in-service conditions. Obtained results showed that different fatigue performance may be expected for various stages of the TBC deposition as well as due to the variation of the deposition process and sample temperature history. © Copyright (2015) by ASM International All rights reserved.

  • 121.
    Parsian, Amir
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Dynamics of Torsional and Axial Vibrations in Indexable Drills2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Drilling is widely used in manufacturing of products which need holes, for example for fluid channels, screws or pins. Depending on application, workpiece material, cutting parameters and economic considerations, different types of drills are employed. Indexable insert drills are types of drills which facilitate inserts to make holes. These types of drills can make high pitch noises due to vibrations. The focus of this thesis is to investigate the mechanism behind these vibrations in order to help reducing the generated noise in the future designs. Primary investigations show that the main mechanism which results the mentioned noise is regenerative chatter vibrations due to axial and torsional flexibilities. There is a gap in modeling of chatter vibrations in indexable drills where loadings and geometries are asymmetrical and due to torsional vibrations, delay terms are variable. The first step of simulating regenerative chatter vibrations in the drill is to model static cutting forces in a reliable way. In this thesis, a model is proposed which is capable of predicting static cutting forces through segmentation of cutting edges. Since, using this model, forces can be calculated separately on each insert, it is possible to consider differences of inserts in estimationof the cutting loads. The obtained loads are used in the chatter simulation.A model is proposed to simulate chatter vibrations by considering axialand angular deflections and the coupling between them. The resulted model isa system of delay differential equations with variable delays. Variations in timedelays, tool jump-outs and backward motions of inserts have been included inthe proposed time-domain simulation. A set of experiments is conducted toverify the model.

  • 122.
    Parsian, Amir
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Magnevall, Martin
    AB Sandvik Coromant, SE-811 81 Sandviken, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    A Mechanistic Approach to Model Cutting Forces in Drilling with Indexable Inserts2014In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 24, no 0, p. 74-79Article in journal (Refereed)
    Abstract [en]

    Holes are made in many industrial parts that need screws, pins or channels for passing fluids. The general method to produce holes in metal cutting is by drilling operations. Indexable insert drills are often used to make short holes at a low cost. However, indexable drills are prone to vibrate under certain circumstances, causing vibrations that affect tool life. Therefore, a good prediction of cutting-forces in drilling is important to get a good description of the cutting process for optimization of tool body and insert design. Reliable simulations of dynamic forces also aid in prediction of chatter vibrations that have significant effects on the quality of the manufactured parts as well as the tool life. In this paper, a mechanistic approach is used to model the cutting-forces. Cutting-force coefficients are identified from measured instantaneous forces in drilling operations. These coefficients are used for simulating torque around drill-axis, axial force and cutting-forces in the plane perpendicular to drill-axis. The forces are modeled separately for peripheral and central insert, which results in a detailed description of the cutting-forces acting on each insert. The forces acting on each insert are estimated by dividing the cutting edges into small segments and the cutting-forces acting on each segment are calculated. The total forces are predicted by summation of the forces acting on each segment. Simulated torque and forces are compared to measured cutting-forces for two different feeds. A good agreement between predicted and experimental results, especially in torque and axial-force, is observed.

  • 123.
    Parsian, Amir
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Magnevall, Martin
    AB Sandvik Coromant, SE-811 81 Sandviken, Sweden..
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Time Domain Simulation of Chatter Vibrations in Indexable Drills2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 89, no 1-4, p. 1209-1221Article in journal (Refereed)
    Abstract [en]

    Regenerative chatter vibrations are common in drilling processes. These unwanted vibrations lead to considerable noise levels, damage the quality of the workpiece, and reduce tool life. The aim of this study is to simulate torsional and axial chatter vibrations as they play important roles in dynamic behavior of indexable insert drills with helical chip flutes. While asymmetric indexable drills are not the focal points in most of previous researches, this paper proposes a simulation routine which is adapted for indexable drills. Based on the theory of regenerative chatter vibration, a model is developed to include the asymmetric geometries and loadings that are inherent in the design of many indexable insert drills. Most indexable insert drills have two inserts located at different radial distances, namely central and peripheral inserts. Since the positions of the central and peripheral inserts are different, the displacement and thereby the change in chip thickness differs between the inserts. Additionally, the inserts have different geometries and cutting conditions, e.g., rake angle, coating, and cutting speed, which result in different cutting forces. This paper presents a time-domain simulation of torsional and axial vibrations by considering the differences in dynamics, cutting conditions, and cutting resistance for the central and peripheral inserts on the drill. The time-domain approach is chosen to be able to include nonlinearities in the model arising from the inserts jumping out of cut, multiple delays, backward motions of edges, and variable time delays in the system. The model is used to simulate cutting forces produced by each insert and responses of the system, in the form of displacements, to these forces. It is shown that displacements induced by dynamic torques are larger than those induced by dynamic axial forces. Finally, the vibration of a measurement point is simulated which is favorably comparable to the measurement results.

  • 124.
    Parsian, Amir
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Magnevall, Martin
    AB Sandvik Coromant, SE-811 81 Sandviken, Sweden..
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Time-Domain Modeling of Torsional-Axial Chatter Vibrations in Indexable Drills with Low Damping2015Conference paper (Refereed)
  • 125.
    Pejryd, Lars
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Minimization of chatter in machining by the use of mobile platform technologies2012In: Proceedings of the 5th International Swedish Production Symposium, SPS12: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping, 2012, p. 179-189Conference paper (Other academic)
  • 126.
    Rissanen, Sofia
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Soto, Carolina
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Implementering av 5S på Rybergs Charkuteri AB2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis has been performed at Rybergs Charkuteri AB in Uddevalla. Rybergs produce charkuteries locally and one of their products is the well-known sausage Uddevallare. Re-cently they introduced new sausages such as chorizo and pusztagrillar. The 5S-work was implemented at the company as it showed lack of structure and order amongst important materials. The lack of structure affects important spare parts for machines as well as for work tools. The 5S-method is a tool that origins from The Toyota Production System. It eliminates and minimizes waste.

    To reach implementation of the 5-S method all staff at Rybergs participated in training. The training took place in an early stage to give a theoretical knowledge about all steps to the employees. Step one was performed in all production departments. The other steps were performed at two departments. The remaining S-steps were sectioned into smaller areas of two departments in the business. The aim of this work was to streamline Ryberg through a structured implementation of the 5S.

    A qualitative study was performed by methods like open interviews and observations. To create a deeper understanding, the authors spent a large part of their time in the company which resulted in increased collaboration from the staff. For inspiration and facts about a real implementation the authors conducted a benchmark in the company Parker Hannifin in Trollhättan.

    The authors believe that the work was successfully implemented and mark this success to important spare parts and other important materials that got a standardized markup. The structures of the implemented services were improved and areas of the business got more efficient. The staff provided participation and involvement which set the foundation for suc-cessful work. The organization of spare parts and tools generated inspiration for continued 5S-work.

  • 127.
    Ru, Tao
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Spray Parameters Influence on Suspension Plasma Sprayed Zirconia coatings properties2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Thermal barrier coatings (TBCs) are a simple and proven method to protect hot section components. Suspension Plasma Spray (SPS), an emerging process technology to generate TBCs, compared with traditional Atmospheric Plasma Spray APS, can deposit thinner coat-ings with finer microstructure. Operating parameters play an important role in developing certain properties of coating. In this thesis work, power level, gas flow rate, number of spray-ing strokes, spray gun's nozzle size i.e. internal diameter and suspension rate were controlled to produce coatings with different microstructures and porosity levels. According to the ex-perimental results, the power level of plasma gun play an essential role on coating micro-structure, for instance, the density of vertical cracks increased with growing the power level. The number of spraying strokes showed also an impact on coating porosity. However, due to different nozzle sizes i.e. diameter, the same coating property were controlled by different operating parameters. For coatings deposited by small and large nozzles, their coating thick-ness and roughness mainly relied on power level and gas flow rate. In contrary, it seems that the coating roughness was not influenced by the same parameters when it was deposited by medium nozzle. Also, gas flow rate do not have as big as influence on coating thickness

  • 128.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    HVAF thermal spray Fe-based coating: An environmentally acceptable alternative to cobalt-based coating2015Conference paper (Refereed)
    Abstract [en]

    Fe-based coatings were widely used in the corrosive environment of various indus-tries. It was replacing expensive cobalt-based alloys, which face a ban in the future due to serious health and environmental risks. The aim of the present work was to compare low temperature corrosion behavior of some Fe- and Co-based coatings produced by High-Velocity Air Fuel (HVAF) thermal spraying. Polarization and elec-trochemical impedance spectroscopy (EIS) tests were carried out in 3.5 wt.% NaCl solution at 25°C. The microstructures were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM) to characterize the morphologies of both Fe- and Co-based coatings and analyze the exposed products along the surface and cross-section of specimens. The results revealed that the high-chromium Fe-based coating protected the underlying substrate better than Co-based coating.

  • 129.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Research Environment Production Technology West. Amirkabir University of Tehran, Tarbiat Modares University of Tehran.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Corrosion performance of bi-layer Ni/Cr2C3–NiCr HVAF thermal spray coating2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 369, p. 470-481Article, review/survey (Refereed)
    Abstract [en]

    The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3–NiCr coatings, and C: bi-layer Ni/Cr2C3–NiCr coating) was comparatively studied using immersion,salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3–NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3–NiCr and singlelayerCr2C3–NiCr coatings were around 194 and 38 k cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.

  • 130.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Dizdar, S.
    Höganäs AB, Höganäs.
    Corrosion behavior of high-chromium Fe-based coatings produced by HVAF thermal spraying technique2015Conference paper (Refereed)
    Abstract [en]

    Fe-based coatings with different Cr content were prepared by high-velocity air fuel (HVAF) spraying on the surface of both carbon steel and stainless steel 304L. The corrosion behavior of the coatings were evaluated using polarization and electrochemical impedance spectroscopy (EIS) techniques in 3.5 wt.% NaCl solution. Microstructure of the coatings were evaluated by X-ray diffraction (XRD), optical microscopy (OM), scanning election microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS) before and after corrosion testing. The experimental results indicated that Cr strongly increased the corrosion resistance of the coating. Furthermore, having an elemental composition closer to that of the substrate, the coatings showed lower susceptibility to galvanic corrosion, accordingly lower corrosion rate.

  • 131.
    Sari, Mohammed
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sandsten, Jerker
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Responsive Web Design: Ur ett utvecklar- och användarperspektiv2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Today, mobile devices and tablets populate the market. Developing websites for different platforms could often be expensive and time consuming. Responsive web design (RWD) is a new design approach that aims to provide a better experience across many different devices. The design method modifies the viewing screen size, allowing different presentations of the context depending on the device used. In this study, five designers have been interviewed to understand their experience of RWD. The questions were based on how the designers apply the method, the most important aspects with RWD and their general opinion. The recent expansion of mobile devices forces designers to implement new methods to improve the mobile experience. Besides the interviews, a survey took place to gather a public opinion regarding mobile websites. The survey would make it easier to understand what the end-user likes and dislikes about the current way of displaying contents on mobile devices and tablets. The study revealed both pros and cons that makes RWD what it is today. The result will hopefully make it easier for future developers to make the right decisions when developing a multiplatform-based responsive website.

  • 132.
    Segerstark, Andreas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Additive Manufacturing using Alloy 718 Powder: Influence of Laser Metal Deposition Process Parameters on Microstructural Characteristics2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive manufacturing (AM) is a general name used for production methodswhich have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final component is achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study.Laser metal deposition using powder as an additive (LMD-p) is an AM processwhich uses a multi-axis computer numerical control (CNC) machine or robot toguide the laser beam and powder nozzle over the deposition surface. Thecomponent is built by depositing adjacent beads layer by layer until thecomponent is completed. LMD-p has lately gained attention as a manufacturing method which can add features to semi-finished components or as a repair method. LMD-p introduce a low heat input compared to arc welding methods and is therefore well suited in applications where a low heat input is of an essence. For instance, in repair of sensitive parts where too much heating compromises the integrity of the part.The main part of this study has been focused on correlating the main processparameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance and that these parameters has a significant effect on the dimensionalcharacteristics of the material such as height and width of a single deposit as wellas the straightness of the top surface and the penetration depth.To further understand the effects found in the material, temperaturemeasurements has been conducted using a temperature measurement methoddeveloped and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the emitted laser light on the thermocouples.

  • 133.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Economical Viability of Laser Metal Deposition2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Reports on large economic savings using Additive Manufacturing (AM) has been found in literature when exploiting the positive capabilities of AM. This paper evaluates the economic potential of, the AM method, laser metal deposition (LMD) in production of add-on features compared to conventional manufacturing methods. This is done by theoretical case studies, which explore factors critical to the cost of manufacturing a jet engine flange. LMD has the potential to be an economical viable alternative to conventional manufacturing methods when the manufactured component has a high buy-to-fly ratio, the component is small and complex, if the operator time can be kept to a minimum, and/or when the design freedom of LMD can be capitalized into lighter and more efficient components.

  • 134.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Evaluation of a temperature measurement method developed for laser metal deposition2017In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 22, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Measuring temperatures in the material during laser metal deposition (LMD) has an inherent challenge caused by the laser. When thermocouples are radiated by the high intensity laser light overheating occurs which causes the thermocouple to fail. Another identified difficulty is that when the laser passes a thermocouple, emitted light heats the thermocouple to a higher temperature than the material actually experience. In order to cope with these challenges, a method of measuring temperatures during LMD of materials using protective sheets has been developed and evaluated as presented in this paper. The method has substantially decreased the risk of destroying the thermocouple wires during laser deposition. Measurements using 10 mm2 and 100 mm2 protective sheets have been compared. These measurements show small variations in the cooling time (∼0.1 s from 850°C to 500°C) between the small and large protective sheets which indicate a negligible effect on the temperature measurement. © 2016 Institute of Materials, Minerals and Mining.

  • 135.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Evaluation of the effect of process parameters on microstructural characteristics in laser metal deposition of Alloy 7182015In: Journal of optics and laser technologyArticle in journal (Refereed)
  • 136.
    Segerstark, Andreas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Review of Laser Deposited Superalloys Using Powder as an Additive2014In: 8th International Symposium on Superalloy 718 and Derivatives: Conference Proceedings / [ed] Ott, E., Banik, A., Andersson, J., Dempster, I., Gabb, T., Groh, J., Heck, K., Helmink, R., Liu, X. & Wusatowska-Sarnek, A, Hoboken, NJ, USA: John Wiley & Sons, 2014, p. 393-408Conference paper (Refereed)
  • 137.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Heat input and temperatures in welding2013In: JOM-17 - International Conference on Joining Materials, JOM-Institute , 2013Conference paper (Refereed)
    Abstract [en]

    A key feature in welding is the energy supplied, in order to join the work pieces together. For all fusion welding methods, the supplied energy is so high that the work-piece joint surfaces are melted and fused together. The energy supplied is then transported away, mainly by conduction through the base materials. The temperature of the weld decreases and a solid joint is eventually formed. This may then undergo phase transformations and finally the weld joint reaches ambient temperature.

    The thermal history of a welded joint has a large effect on the microstructure and mechanical properties. Welding metallurgist therefore consider the cooling time t8/5 as crucial to understand the resulting properties of a joint in steel structures. The cooling time is influenced by several factors, like heat input, base material thickness, base material thermal properties, preheat an interpass temperatures etc. Regarding the heat input, the efficiency of the welding arc has for a long time been debated, i.e. how much of the arc energy really goes into the weld. Large efforts are being made to measure this very accurately.

    Another significant research field has been to measure or calculate the cooling time of welds, in particular t8/5. However, this cooling time is affected by the arc energy and by the arc efficiency.

    In a more macroscopic sense, it has been shown that the temperature of a welded structure can vary with the presence of for example internal heat sinks. Such variations may affect macroscopic properties like penetration. One way to ensure constant condition in terms of temperature could be to increase the heat input if the temperature decreases. However, how such variations affect for example the cooling rate has not been studied.The aim of the present paper is to report some experimental results regarding cooling rate in welded joints and put this into context of arc efficiency and temperature regulations and also discuss how the cooling rate may be affected in more production like welding situations.

  • 138.
    Singh Handa, Sukhdeep
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Precipitation of Carbides in a Ni-based Superalloy2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Alloy B is relatively new precipitation hardening superalloy. It´s applications are in the hot sections of the aero engines, rocket nozzles, gas turbines and in the chemical and petro-leum applications. The alloy is characterized by keeping high strength at elevated tempera-tures and high creep resistance. It´s excellent mechanical properties and corrosion resis-tance are due to the balanced amount of the coherent γ' matrix, combined with other alloy-ing elements and carbides.

    There are three types of carbides which can be found in nickel-based superalloys: MC, M

    23C6 and M6C. Primary MC carbides act as source of carbon for the secondary carbides, which precipitate at the grain boundaries. They can have strengthening effect by hindering the movement of dislocations.

    In this work both simulation and experimental analysis are conducted in order to investi-gate the behaviour of the secondary carbides. JMatPro simulation is used to predict the behaviour of the material. Heat treatments are conducted at soak temperatures ranging from 920 °C to 1130 °C, with steps of 30 °C, and dwell times of 0.5, 1, 2 and 24 hours. Experimental methods included analysis at LOM, SEM, EDS, manual point counting and hardness tests.

    Main results show chromium rich M

    23C6 carbides are stable at lower temperature compared to molybdenum rich M6C. Both appear as fine and discrete particles at the grain boundaries at 1070 °C. This morphology is believed to be beneficial for the mechanical properties of the alloy. The volume fraction varies between 0.6 and 1.3%. Hardness values are relevant in the range of 920-1010 °C. Above this range there is sudden drop of the hardness

  • 139. Sjöberg, Göran
    et al.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjunnesson, Anders
    New Materials in the Design and Manufacturing of Hot Structures for Aircraft Engines: Allvac 718Plus2009In: XIX International Symposium on Air Breathing Engines 2009: ISABE 2009, Montreal, Canada, 7-11 September, 2009., Reston, VA: American Institute of Aeronautics and Astronautics, 2009, Vol. 3, p. 1406-1415Conference paper (Refereed)
  • 140.
    Sokolowski, Pawel
    et al.
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Musalek, Radek
    Inst Plasma Phys CAS, Dept Mat Engn, Vvi, Slovankou 3, Prague 18200, Czech Republi.
    Candidato, Rolando T. Jr.
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, France.
    Pawlowski, Lech
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Nait-Ali, Benoit
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Smith, David
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Thermophysical properties of YSZ and YCeSZ suspension plasma sprayed coatings having different microstructures2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 28-38Article in journal (Refereed)
    Abstract [en]

    The paper describes the ceramic top coats of Thermal Barrier Coatings (TBC) obtained by Suspension Plasma Spraying (SPS). The spray process realized with different plasma torches allowed obtaining coatings having different morphology, namely, columnar-like and two-zones microstructure. The microstructures influenced the thermal transport properties of TBC’s. The study analyses the thermophysical properties of yttria and yttria- with ceria- stabilized zirconia coatings, i.e. YSZ and YCeSZ, respectively. The spray processes were realized with the use of three different plasma spray torches: (i) SG-100; (ii) Axial III and (iii) hybrid WSP one. The deposition parameters were designed for each plasma torch separately. The microstructure of coatings was then analyzed using Optical and Scanning Electron Microscopy i.e. OM and SEM, respectively. The thermophysical properties of the coatings such as density, specific heat and thermal dilatation were measured using gas pycnometry, calorimetry and dilatometry methods respectively. The collected data were used, together with thermal diffusivity found with the use of laser flash method, to calculate the thermal conductivity of the deposits. The thermal conductivities of coatings were in a range from 0.63 to 0.99 [W/m.K] for YSZ samples and between 0.82 and 1.37 [W/m.K] in the case of YCeSZ coatings. Thermal transport properties were found to be influenced by the coatings’ porosity and their microstructure. Finally, the thermal conductivity values were successfully validated using response function method, which can be an alternative to complex FEM methods. (C) 2017 Elsevier B.V. All rights reserved.

  • 141.
    Soto, Carolina
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Rissanen, Sofia
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Implementering av 5S på Rybergs Charkuteri AB2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis has been performed at Rybergs Charkuteri AB in Uddevalla. Rybergs produce charkuteries locally and one of their products is the well-known sausage Uddevallare. Re-cently they introduced new sausages such as chorizo and pusztagrillar. The 5S-work was implemented at the company as it showed lack of structure and order amongst important materials. The lack of structure affects important spare parts for machines as well as for work tools. The 5S-method is a tool that origins from The Toyota Production System. It eliminates and minimizes waste.

    To reach implementation of the 5-S method all staff at Rybergs participated in training. The training took place in an early stage to give a theoretical knowledge about all steps to the employees. Step one was performed in all production departments. The other steps were performed at two departments. The remaining S-steps were sectioned into smaller areas of two departments in the business. The aim of this work was to streamline Ryberg through a structured implementation of the 5S.

    A qualitative study was performed by methods like open interviews and observations. To create a deeper understanding, the authors spent a large part of their time in the company which resulted in increased collaboration from the staff. For inspiration and facts about a real implementation the authors conducted a benchmark in the company Parker Hannifin in Trollhättan.

    The authors believe that the work was successfully implemented and mark this success to important spare parts and other important materials that got a standardized markup. The structures of the implemented services were improved and areas of the business got more efficient. The staff provided participation and involvement which set the foundation for suc-cessful work. The organization of spare parts and tools generated inspiration for continued 5S-work.

  • 142.
    Svensson, Lars-Erik
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Harati, Ebrahim
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Increasing fatigue life using Low Transformation Temperature (LTT) welding consumables,2013In: 2nd Swedish conference on design and fabrication of welded structures: Conference proceedings / [ed] Zuheir Barsoum, Stockholm, 2013, p. 49-64Conference paper (Other academic)
  • 143.
    Svensson, Lars-Erik
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Ohlsson, A. R.
    SSAB AB, Oxelösund, Sweden.
    Stemne, D.
    SSAB AB, Oxelösund, Sweden.
    Gustafsson, M.
    ESAB AB, Göteborg, Sweden.
    Bengtsson, P.
    AGA Gas AB, Stockholm, Sweden.
    Strength and Impact Toughness of High Strength Steel Weld Metals: Influence of Welding Method, Dilution and Cooling Rate2015In: Proceedings of IIW International Conference, High-Strength Materials: Challenges and Applications, 2-3 July 2015, Helsinki, Finland, Helsingfors, 2015, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Producing welds with properties matching those of the steel is a challenge at high strength levels. The present study has investigated how the choice of welding method affects weld metal mechanical properties through effects on dilution and cooling rate. Butt welds were produced in 12 mm plates in 777 MPa and 1193 MPa yield strength steels. Conventional arc welding methods including manual metal arc, gas metal arc welding, rapid arc welding and submerged arc welding were used as well as laser-gas metal arc hybrid welding. Filler materials with nominal yield strengths between 810 and 1000 MPa were used. Cooling times between 800 C and 500 C were varied between 5s and 15s and measured by insertion of thermocouples into the weld pool.High quality welds were produced efficiently with all welding methods even though dilution varied between 3%, for manual metal arc welding, to 73% for laser-hybrid welding. Low dilution, rapid cooling and single pass welding contributed to higher strength. Overmatching weld metal strength was achieved for the less strong steel and weld yield strengths of >1000 MPa were recorded for the stronger steel. Fracture in transverse tensile testing was always located in base material or HAZ. Impact toughness was higher for lower strength and low dilution. Results are discussed relating choice of welding method and cooling rate to weld metal properties for different steel strength levels.

  • 144.
    Svenungsson, Josefine
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Choquet, Isabelle
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Kaplan, Alexander F.H.
    Luleå University of Technology, Department of Engineering Science and Mathematics, 971 87 Luleå, Sweden.
    Laser Welding Process: A  Review of Keyhole Welding Modelling2015In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 78, p. 182-191Article in journal (Refereed)
    Abstract [en]

    Laser welding is used in several industrial applications. It can be distinguished between conduction mode and keyhole mode welding, between pulsed wave and cw laser welding and between CO2-lasers with a wavelength of 10 μm and various laser types of about 1 μm wavelength. A deeper understanding of laser welding allows improving weld quality, process control and process efficiency. It requires a complementary combination of precise modelling and experimental investigations. The here presented review focuses on modelling of laser keyhole welding, for both wavelength regimes. First, the fundamentals of the laser welding process and its physics such as beam propagation, keyhole formation and melt pool dynamics are addressed. The main approaches for modeling energy transfer from laser beam to keyhole surface as well as fluid flow in the material are then discussed. The most relevant publications are systematically structured, particularly categorized with regard to the respective physical phenomena addressed. Finally some open questions are underlined.

  • 145.
    Tan, Ruoyo
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Protective coatings for Al press tools used in automotive industry2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The application of the thermally sprayed WC-Co and Cr 3C2-NiCr coatings have been widely used in industry for its superior sliding, abrasive and erosive wear properties. The Al2O3 coating possessing high hardness can be utilized to improve the wear resistance of the metallic surface. Replacing the stamping tool material from steel to lightweight aluminium with protective coatings offers significant gains such as reduction in power costs and increasing operational efficiency during manufacturing of sheet automobile parts. In this study, the WC-CoCr and Cr3C2-NiCr coatings were sprayed with High Velocity Air-Fuel (HVAF) process and Al2O3 coating was deposited using Atmosphere Plasma Spraying (APS) process. The coatings were evaluated and compared based on the results of roughness tests, hardness tests, adhesion tests, quantitative imaging analysis and microstructure analysis. The experimental results revealed that the roughness value varied in a lower range which implies of a high density of the coatings. It was found that coatings have an extremely high hardness value as tested by the Vickers hardness test. The WC-Co coating was found to be the hardest (1215.2HV). The adhesion test was implemented according to the ASTM C633-79 standard. The result showed that WC-Co and Cr3C2-NiCr coatings without a bond coat had high tensile strength, higher than the respective glue strength (63.54MPa, 75.89MPa). Whereas, the Al2O3 coating has a much lower tensile strength (15.2MPa, 25.68MPa, with and without bond) than others and using a bond coat layer does not contribute to an increase in adhesion strength of the cermet coatings. The coating thickness was evaluated using Light Optical Microscopy (LOM) and microstructure analysis was carried out using Scanning Electron Microscopy (SEM). From the microstructure analysis, it was observed that all the coatings have a dense microstructure, very low porosity and low oxide inclusions in top coat. The WC and Cr3C2 grains retain a large volume fraction of finely dispersed in matrix. The alumina coating was found to have low levels of un-melted or the re-solidified particles in the coating. All of the aforementioned analysis and results reveal that WC/CoCr and Cr3C2-NiCr coating show promising potential for press tool applications. However, abrasive resistance test still remained to be done and will be performed in the future. The result of it can reveal the actual wear resistance between two coatings in reality and will be helpful in determining the better protective coating for aluminium press tools

  • 146.
    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.

  • 147.
    Tuyishimire, Gabriel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Utvärdering av osäkerhet i sprickfortplantningsmodeller2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In aerospace industry and other major mechanical industry systems, engineering components that are subjected to cyclic loads often lead to progressive crack growth that eventually results in struc-tural fracture. The damage tolerance design which is based on the assumption of pre-existed flaws in a structure is an important approach in aircraft industry since it is impossible to have flaw-free manufactured components.In this thesis work, an evaluation of crack propagation models was carried out. Fatigue crack growth threshold and fatigue crack growth rate models were evaluated. A method to present ex-perimental data available was developed to evaluate uncertainties in fatigue life models for more accurate predictions. Currently, a software that is used for predicting crack propagation life is NASGRO. The study has been made for two types of materials: a nickel-iron-based alloy (Inconel 718 forging) and titanium alloys (Ti 6-4 both forging and casting).A threshold model is in the normal case developed for each temperature. A method to model fatigue threshold (ΔKth) has been suggested by assuming temperature independence of ΔKth. In this method, a new threshold model was created by making use of an A/P (Actual/Predicted) plot so that all measured threshold values are on the conservative side of the minimum model. With this method, an understanding of fatigue threshold model was improved over the other method due to the possibilities to model ΔKth with average and minimum threshold values for each load ratio (ΔKth, R).Moreover, a method to investigate which set of parameters that best represent the crack growth behaviour has been suggested. In this method the best set of parameters were chosen to be the set of parameters giving the best fit to the available (da/dN, ΔK) points. The comparison between this method and the method with the set of parameters that give minimum scatter in the A/P values was done.Crack growth rate da/dN log curves were plotted as function of stress intensity range ΔK for R-ratio values ranging from -2 to 0.9 for the two different methods. A distinctive difference between the two methods was observed in Paris region at high temperatures (5500C-6500C) which becomes more obvious at lower R-ratios. Predicting crack propagation rate model with set of parameters giving minimum standard deviation in da/dN points was shown to be less conservative than that of parameter sets giving lowest scatter in A/P. Using both evaluation methods, da/dN versus ΔK plots of Inconel718forging were compared to da/dN (ΔK) plots for the pre-existing data at 5500C for R-ratios ranging from 0 to 0.8. An overall R-ratio influence was observed throughout for both ΔKth and da/dN.

  • 148.
    Valiente Bermejo, María Asunción
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Guia de les escultures de Mollet del Vallès: Metalls, tècniques i curiositats2015 (ed. 1)Book (Other (popular science, discussion, etc.))
    Abstract [en]

    This publication presents a comprehensive study on the current 35 metal artwork pieces located in public spaces of Mollet del Vallès. The sculptures are described from a technical perspective: metallic alloys, joining techniques and protective mechanisms against corrosion are described. However, this research also reveals interesting curiosities and secrets hidden by these sculptures. The information is organised in clear datasheets, where the technical details from the experimental observation and from the official technical project reports are summarised. The symbolisms, anecdotes and curiosities included in this work were gathered during fruitful conversations with authors, authorities and companies involved in the execution of the metal works. The main aim of this work is to invite the reader to stroll into town, to rediscover our heritage, to appreciate it and to make new generations love it. 

  • 149.
    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.

  • 150.
    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.

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