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  • 301.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    University West, Department of Engineering Science.
    Characterization of Cold Lap Defects in Tandem Arc MAG Welding2010In: Proceedings of the International Conference on Advances in Welding Science & Technology for Construction, Energy & Transportation AWST-2010: Istanbul, Turkey, 12-15 July, 2010, 2010, p. 303-311Conference paper (Refereed)
  • 302.
    Li, Peigang
    et al.
    University West, Department of Engineering Science.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Factors influencing fusion of spatter to the base metal during tandem GMAW2012In: Proceedings of The 5th International Swedish Production Symposium: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping, Sweden, 2012, p. 233-239Conference paper (Refereed)
    Abstract [en]

    Tandem gas metal arc welding (tandem GMAW) is, as a high productivity welding method of manufacturing process, utilized broadly in modern Swedish industry. Spatter is more or less an inevitable flaw in GMAW, especially for the high efficiency processes. Recently, spatter was found as a potential source of cold laps, which negatively influences fatigue life. The main objectives of this paper are to investigate the spatter/base metal interface and identify the primary factors for formation of cold laps.

    Tandem GMAW was performed in a sealed chamber filled with either pure argon or pure dioxide. Cross sections of spatter and base metal were prepared and evaluated by Light optical microscopy and Scanning Electron Microscopy (SEM) with an attached Energy Dispersive Spectroscope (EDS).

    Mn-Si oxides were found to enhance the lack of fusion occurrence in the spatter/base metal. The oxide of Mn and Si mostly came from oxidation of the droplets in the welding process. Spatter diameter and spatter distance was evaluated with respect to lack of fusion in spatter/base metal interface for welds using pure Ar shielding gas. From this it was concluded that temperature is another important factor for lack of fusion formation in the spatter/base metal interface.

  • 303.
    Li, Peigang
    et al.
    University West, Department of Engineering Science.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Factors influencing fusion on spatter to the base metal during tandem GMAW weldingArticle in journal (Refereed)
  • 304.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Influence of oxides on cold lap formation in tandem GMAW2012In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 17, no 8, p. 643-648Article in journal (Refereed)
    Abstract [en]

    The connection between the formation of cold laps and the presence of Mn‐Si oxides was studied. The underlying purpose is to understand the fundamental mechanisms of cold lap formation and to avoid it. Tandem gas metal arc welding (GMAW) was used to produce welded specimens in two different shielding gases (pure Ar and pure CO2) with base metal S355 MC (EN-10149-2) and wire G3Si1 (EN ISO 14341-A). Cross-sections of welds in the cold lap location were evaluated by light optical microscopy and scanning electron microscopy combined with energy dispersive spectroscopy. The results showed that the Mn‐Si oxides significantly enhanced cold laps formation, especially the overlap type cold lap formation. The Mn‐Si oxides originated from oxidation of the droplets. These oxides transfers to the surface of the weld pool at the weld toe, where they contributed to the formation of the cold laps.

  • 305.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Influence of preheating temperature on cold lap formation in tandem GMAW2013Conference paper (Other academic)
    Abstract [en]

    A cold lap is defined as a type of micro-lack of fusion in ISO standard (ISO 6520-1:2007) and have been found to influence fatigue properties of welds significantly. In the present study, the main purpose was to investigate the influence of preheating temperature on cold lap formation in tandem GMAW, both with respect to dimensions and occurrence probabilities.

    Three different preheating temperatures were applied and cross-sections of welds were evaluated by light optical microscopy. The results showed that the cold lap occurrence frequency is a function of base metal temperature. However, the base metal temperature does not have a significant influence on cold lap depth.

  • 306.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Study on temperature influence on lack of fusion formation in spatter/base metal interface2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 875 - 877, p. 1421-1428Article in journal (Refereed)
    Abstract [en]

    In the development of modern welded structures with longer life-time and/or higher load-carrying ability, fatigue properties are becoming more and more important. A lot of researches have been done to investigate which factors can elongate the fatigue life of weldments. Cold lap defects, were found to be important initiation sites of the fatigue failure in 1990s. In the ISO standard, cold lap is referred to as a type of micro-lack of fusion. Previous study found that most of the cold laps in GMAW process are formed in spatters. In this paper the interface of spatter/base metal was cut, polished and investigated by conventional metallographic methods. The aim is to reveal the influence of temperature on cold lap formation. In the experiments, different pre-heating temperatures of the parent plate were used in tandem GMAW. Results showed linear empirical relationship between the temperature of the parent plate and the amount of lack of fusion in the spatter/base metal interface.

  • 307.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    Department of Materials and manufacture, Chalmers University.
    Characterization of cold lap defects in tandem arc MAG welding2012In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 56, no 9/10, p. 20-25Article in journal (Refereed)
    Abstract [en]

    The objective of this investigation was to classify and characterize the small lack of fusion defects, called cold lap, located at the weld toe. Since the defects are very small (0.01–1.5 mm) and difficult to detect by NDT methods, a better understanding of the formation mechanism is required to be able to avoid their formation. The investigation consisted of two parts. Firstly, a study was made on the type and frequency of cold laps. Three types were identified, namely “spatter cold lap”, and “overlap cold lap” and “spatter-overlap cold lap”. No relation between type or frequency of cold laps and the welding parameters could be established. Secondly, the interface between spatter and the base material was investigated using optical and scanning electron microscopy, to better understand the cold lap formation mechanism. Manganese-silicate particles were found in the interface located in such a way that they may assist cold lap formation.

  • 308.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    Chalmers University of Technology, Materials and Manufacturing Technology.
    Characterization of cold lap defects in tandem arc MAG welding2013In: Rivista Italiana della Saldatura, ISSN 0035-6794, Vol. 65, no 5, p. 761-769Article in journal (Refereed)
    Abstract [en]

    The objective of this investigation was to classify and characterize the small lack of fusion defects, called cold lap, located at the weld toe. Since the defects are very small (0.01-1.5 mm) and difficult to detect by NDT methods, a better understanding of the formation mechanism is required to be able to avoid their formation. The investigation consisted of two parts. Firstly, a study was made on the type and frequency of cold laps. Three types were identified, namely "spatter cold lap", and "overlap cold lap" and "spatter-overlap cold lap". No relation between type or frequency of cold laps and the welding parameters could be established. Secondly, the interface between spatter and the base material was investigated using optical and scanning electron microscopy, to better understand the cold lap formation mechanism. Manganese-silicate particles were found in the interface located in such a way that they may assist cold lap formation.

  • 309.
    Lindgren, Lars-Erik
    et al.
    Luleå University of Technology, Luleå, Sweden.
    Lundbäck, Andreas
    Luleå University of Technology, Luleå, Sweden.
    Fisk, Martin
    Malmö University, Malmö, Sweden,.
    Pederson, Robert
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Simulation of additive manufacturing using coupled constitutive and microstructure models2016In: Additive manufacturing, ISSN 2214-8604, Vol. 12, no Part B, p. 144-158Article in journal (Refereed)
    Abstract [en]

    The paper describes the application of modeling approaches used in Computational Welding Mechanics (CWM) applicable for simulating Additive Manufacturing (AM). It focuses on the approximation of the behavior in the process zone and the behavior of the solid material, particularly in the context of changing microstructure. Two examples are shown, one for the precipitation hardening Alloy 718 and one for Ti-6Al-4V. The latter alloy is subject to phase changes due to the thermal cycling

  • 310. 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)
  • 311.
    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

  • 312.
    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.

  • 313.
    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)
  • 314.
    List, A
    et al.
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Production Engineering.
    Villa, M
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Gärtner, F
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Klassen, T
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Mechanical properties of cold-sprayed Ti-6Al-4V coatings2013In: Proceedings of the International Thermal Spray Conference, ASM International, 2013, p. 155-160Conference paper (Refereed)
    Abstract [en]

    Titanium and titanium alloys are of great interest in aerospace and medical industries. Especially, Ti-6Al-4V alloys show a unique combination of high mechanical strength, low density and an outstanding corrosion resistance. However, particularly the high strength restricts industrial processing procedures. Thus, there are increasing demands for powder metallurgical process routes. For pure titanium, cold spraying already proved to be a promising alternative for manufacturing semi-finished products, mainly due to the use of high process gas temperatures and pressures. Nevertheless, due to the higher material strength, the production of Ti-6Al-4V coatings by cold spraying is still challenging, even under higher process parameters. The present study deals with the production and characterization of Ti-6Al-4V coatings produced by cold spraying. All experiments were performed using nitrogen as process gas. By a systematic variation of the spray parameters up to a process gas temperature of 1000°C and a process gas pressure of 5 MPa, the coatings could be tuned for optimum mechanical properties. In addition, attainable coating properties are described in terms of a newly introduced coating quality parameter η, namely the ratio of the particle velocity to the critical velocity, to reveal the most significant influences on coating performance and to give hints for further optimization.

  • 315.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Production Engineering.
    Adhesion and residual stress characterization of HVOF sprayed inconel 718 coatings2008Doctoral thesis, comprehensive summary (Other academic)
  • 316.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Olika grupper av material med avseende på korrosion, slitage2016Conference paper (Other academic)
  • 317.
    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.

  • 318.
    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.

  • 319.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Dizdar, S.
    Höganäs AB, Höganäs, Sweden.
    Cavitation-erosion resistance of HVAF-sprayed Fe-based metal coatings for marine applications2017Conference paper (Other academic)
  • 320.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 3, p. 380-388Article in journal (Refereed)
    Abstract [en]

    The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young’s modulus and thus a tool for Design Practice for repair applications. © 2013 ASM International.

  • 321.
    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)
  • 322.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    University West, Department of Engineering Science, Division of Production Engineering.
    Sattari, M.
    Characterization of adhesion strenght of HVOF sprayed IN718 coatings2009In: Proceedings of th 22nd Internationa Conference on Surface Modification technolgies - SMT22. Trollhättan, Sweden / [ed] T.S. Sudarshan & Per Nylen, VALAR Docs , 2009, p. 11-18Conference paper (Refereed)
    Abstract [en]

    The tensile adhesion strength of thermally sprayed coating is conventionally evaluated via the ASTM C633-69 standard. The maximum measurable adhesion is then limited by the adhesion strength of the polymer media. High velocity oxy-fuel (HVOF) spraying can exhibit very high bonding strength and thus it is essential to develop an alternative method to evaluate coating adhesion strength. In this work a Modified Tensile Adhesion Test (MTAT) is proposed replacing gluing with induction brazing. The method was evaluated for HVOF sprayed Inconel 718 coatings deposited on Inconel 718 substrates. The effect of induction brazing process and the characteristics of the braze-coating interface was given particular interest. The results indicate that the method is superior to the ASTM C633-69 for characterisation of adhesion of coatings with high bond strength.

  • 323.
    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)
  • 324.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Östergren, L.
    Volvo Aero Corporation, Trollhättan.
    Relationships between process parameters, microstructure, and adhesion strength of HVOF sprayed IN718 coatings2011In: Journal of Thermal Spray Technology, Vol. 20, no 1-2, p. 76-82Article in journal (Refereed)
    Abstract [en]

    Fundamental understanding of relationships between process parameters, particle in-flight characteristics, and adhesion strength of HVOF sprayed coatings is important to achieve the high coating adhesion that is needed in aeronautic repair applications. In this study, statistical Design of Experiments (DoE) was used to identify the most important process parameters that influence adhesion strength of IN718 coatings sprayed on IN718 substrates. Special attention was given to the parameters combustion ratio, total gas mass flow, stand-off distance and external cooling, since these parameters were assumed to have a significant influence on particle temperature and velocity. Relationships between these parameters and coating microstructure were evaluated to fundamentally understand the relationships between process parameters and adhesion strength. © 2010 ASM International.

  • 325.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Sato, K.
    Fujimi Incoporated.
    Houdkova, S.
    University of West Bohemia.
    Smazalova, E.
    University of West Bohemia.
    Lusvarghi, L.
    University of Modena and Reggio Emilia.
    Bolelli, G.
    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 Process2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 331-345Article in journal (Refereed)
    Abstract [en]

    Lowering the thermal energy and increasing the kinetic energyof hard metal particles sprayed by the newly developed HVAF systems can significantly reduce their decarburization, and increases the sliding wear and corrosion resistance of the resulting coatings, making the HVAF technique attractive, both economically and environmentally, over its HVOF predecessors. Two agglomerated and sintered feedstock powder chemistries, WC-Co (88/12) and WC-CoCr (86/10/4), respectively, 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. Their dry sliding wear behaviors and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al<inf>2</inf>O<inf>3</inf> 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 the formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviors were evaluated via standard Neutral Salt Spray, Acetic Acid Salt Spray, accelerated corrosion test, and electrochemical polarization test at room temperature. The optimization of the tribological properties of the coatings is discussed, focusing on the suitable selection of primary carbide size for different working load applications. © 2015 ASM International

  • 326.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Sato, Katu
    Fujimi Incorporated, Japan.
    Screening design of hard metal feedstock powders for supersonic air fuel processing2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, no 15 November, p. 447-457Article in journal (Refereed)
    Abstract [en]

    Replacement of Electrolytic Hard Chromium (EHC) method by Thermal Spray Technology has shown a growing interest 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, a first order process map has been intended via a full factorial Design of Experiments (DoE) to establish relationships between powder feedstock characteristics, such as primary carbides grain size, binder grain size and powder strength, and coatings microstructure and mechanical properties. A second order process map was then established to study possible correlations between the deposit microstructural properties and their respective abrasion/erosion wear and corrosion performances.

  • 327.
    Magnevall, Martin
    et al.
    AB Sandvik Coromant.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Improved cutting force measurements in milling using inverse filtering2016In: Shock & Vibration, Aircraft/Aerospace, Energy Harvesting, Acoustics & Optics, Volume 9: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016 / [ed] Anders Brandt, Raj Singhal, Springer, 2016, Vol. 9_2016, p. 1-11Chapter in book (Refereed)
    Abstract [en]

    Accurate estimates of cutting forces in metal cutting are important in the evaluation of e.g. different cutting tool geometries and concepts. However, dynamic influences from the measurement system affect the measurement result and may make the obtained cutting force data erroneous and misleading. This paper presents a method to construct an inverse filter which compensates for the dynamic influences from the measurement system. Using the suggested approach, unwanted dynamic effects from the measurement system can be counteracted. By applying the inverse filter it is possible to retain information related to the cutting forces at higher frequencies than possible with unfiltered data. The advantage of using the proposed method is illustrated by comparing simulated, inverse-and low-pass filtered cutting forces to unfiltered forces at different cutting speeds. The results indicate that inverse filtering can increase the usable frequency range of the force dynamometer and thereby provide more accurate and reliable results compared to both low-pass and unfiltered force measurements. © The Society for Experimental Mechanics, Inc. 2016.

  • 328.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Functional Performance of Gadolinium Zirconate/Yttria Stabilized Zirconia Multi-Layered Thermal Barrier Coatings2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Yttria stabilized zirconia (YSZ) is the state of the art ceramic top coat material used for TBC applications. The desire to achieve a higher engine efficiency of agas turbine engine by increasing the turbine inlet temperature has pushed YSZ toits upper limit. Above 1200°C, issues such as poor phase stability, high sinteringrates, and susceptibility to CMAS (calcium magnesium alumino silicates) degradation have been reported for YSZ based TBCs. Among the new materials,gadolinium zirconate (GZ) is an interesting alternative since it has shown attractive properties including resistance to CMAS attack. However, GZ has a poor thermo-chemical compatibility with the thermally grown oxide leading to poor thermal cyclic performance of GZ TBCs and that is why a multi-layered coating design seems feasible.This work presents a new approach of depositing GZ/YSZ multi-layered TBCs by the suspension plasma spray (SPS) process. Single layer YSZ TBCs were also deposited by SPS and used as a reference.The primary aim of the work was to compare the thermal conductivity and thermal cyclic life of the two coating designs. Thermal diffusivity of the YSZ single layer and GZ based multi-layered TBCs was measured using laser flash analysis (LFA). Thermal cyclic life of as sprayed coatings was evaluated at 1100°C, 1200°C and 1300°C respectively. It was shown that GZ based multi-layered TBCs had a lower thermal conductivity and higher thermal cyclic life compared to the single layer YSZ at all test temperatures. The second aim was to investigate the isothermal oxidation behaviour and erosion resistance of the two coating designs. The as sprayed TBCs were subjected toisothermal oxidation test at 1150°C. The GZ based multi-layered TBCs showed a lower weight gain than the single layer YSZ TBC. However, in the erosion test,the GZ based TBCs showed lower erosion resistance compared to the YSZ singlelayer TBC. In this work, it was shown that SPS is a promising production technique and that GZ is a promising material for TBCs.

  • 329.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Functional Performance of Gadolinium Zirconate/Yttria Stabilized Zirconia Multi-Layered Thermal Barrier Coatings2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Yttria stabilized zirconia (YSZ) is the state-of-the-art ceramic top coat material used for thermal barrier coating (TBC) applications. Demand for higher efficiency in gas turbine engines has led to a continuous increase in the gas in let temperature. However, this increase in temperature has pushed YSZ to its upper limit. Above1200 °C, issues such as poor phase stability, high sintering rate, and susceptibility to CMAS (Calcium Magnesium Alumino Silicates) degradation limit the durability of YSZ based TBCs. Among the new top coat materials suggested for high temperature TBC applications, gadolinium zirconate (GZ) is an interesting alternative to YSZ since it has shown attractive properties which include a better resistance to CMAS attack. However, GZ has poor thermo-chemical compatibility with the thermally grown oxide (alumina), leading to poor thermalcyclic fatigue performance of single layered GZ TBCs. Therefore, a multi-layered GZ/YSZ based TBC design seems promising. This work presents a new approach of depositing multi-layered (double and triple layered) GZ/YSZ TBCs using the recently developed suspension plasma spray(SPS) process. SPS was employed in this work because of its capability to mimic the electron beam physical vapour deposition (EB-PVD) process in terms of producing columnar microstructured TBCs. Single layer YSZ TBCs were also deposited by SPS process and used as a reference for comparing the functional performance of multi-layered GZ based TBCs. The primary aim of this work was to improve the durability of GZ based multilayered TBCs at high temperatures. Durability tests were performed in the temperature range 1100 °C - 1400 °C under different thermal cyclic test conditions (with and without thermal gradient). The results indicate that multilayered GZ based TBCs improve durability compared to the single layer YSZTBCs at all the test temperatures. Failure analysis of the multi-layered GZ/YSZTBCs revealed spallation within the GZ layer close to GZ/YSZ interface and the reason was believed to be the inferior fracture toughness of GZ. In order to improve the fracture toughness in the region of failure, a composite approach comprising multi-layered GZ+YSZ based TBC was considered. It was shown that the composite GZ+YSZ based TBCs did not improve the thermal cyclic lifetime, although improvement in fracture toughness was observed. As a further extension of this work, the influence of YSZ layer thickness on the durability of GZ/YSZTBCs was investigated. It was shown that an increase in YSZ layer thickness in the GZ/YSZ TBC led to poor durability. Additionally, the other important performance criteria for TBCs, i.e. thermal conductivity, was measured experimentally and compared with the single layer YSZ TBC. It was shown that the GZ based TBCs had lower thermal conductivity than YSZ. The second aim was to investigate and compare the erosion performance of multi-layered GZ based TBCs and single layered YSZ TBCs. In the erosion testconducted at room temperature, the GZ based TBCs showed lower erosion resistance compared to the single layer YSZ TBC. The main reason for this difference was attributed to the inferior fracture toughness of GZ. In case of the composite multi-layered GZ+YSZ based TBC, an improvement in erosion resistance was observed compared to the multi-layered GZ based TBC. Based on the results obtained, this work has demonstrated that SPS is a promising processing technique to produce columnar microstructured TBCs irrespective of the composition (GZ, YSZ, GZ+YSZ). It was also shown that GZ/YSZ multilayered TBCs are promising for high temperature TBC applications due to theirl ow thermal conductivity and high thermal cyclic fatigue lifetime. However, low erosion resistance for certain applications might be an issue for the GZ basedTBCs.

  • 330.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Next generation of thermal barrier coatings for high temperature applications2016Conference paper (Other academic)
  • 331.
    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.

  • 332.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Björklund, Stefan
    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.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Engineered thermal barrier coatings deposited by suspension plasma spray2017In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 209, p. 517-521Article in journal (Refereed)
    Abstract [en]

    Yttria stabilized zirconia (YSZ) is susceptible to CMAS (Calcium Magnesium Alumino Silicates) attack at high temperatures (>1200 °C) which limits its durability. New ceramic materials which can overcome these high temperature challenges are highly desirable. This work investigates the feasibility of depositing two variations of three ceramic layered thermal barrier coatings. The first variation comprised of yttria as the top ceramic layer with gadolinium zirconate (GZ) as the intermediate layer and YSZ as the base layer. The second variation comprised of Yttrium Aluminum Garnet (YAG) as the top layer with gadolinium zirconate as the intermediate layer and YSZ as the base layer. Microstructural analysis of the as sprayed three layered TBCs were performed by SEM/EDS. Columnar microstructures with a relatively dense top layer were obtained in both the variations. The porosity content of the TBCs was measured by water intrusion and image analysis methods. Phase composition of each layer of the as sprayed TBCs was analyzed using XRD. YAG showed an amorphous phase whereas GZ showed a cubic defect fluorite phase and tetragonal phase was observed in YSZ. In the case of yttria, monoclinic and cubic phases were observed. © 2017 Elsevier B.V.

  • 333.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Björklund, Stefan
    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.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Failure analysis of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings subjected to thermal cyclic fatigue2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 689, p. 1011-1019Article in journal (Refereed)
    Abstract [en]

    8 wt.% yttria stabilized zirconia (8YSZ) is the standard ceramic top coat material used in thermal barrier coatings (TBCs) due to its excellent thermo-physical and thermo-mechanical properties. However, above 1200 °C, YSZ has issues such as susceptibility to CMAS (Calcium Magnesium Alumino Silicates) attack and enhanced sintering which could lead to catastrophic failure of the TBC. Pyrochlores of rare earth zirconate composition such as gadolinium zirconate have shown to be resistant to CMAS attack and at the same time possess several other attractive properties. However, poor thermal cycling life of single layer gadolinium zirconate (GZ) TBC compared to single layer YSZ has been reported. Therefore, a double layered GZ/YSZ TBC with YSZ as the intermediate coating and GZ as the top coat and a single layer 8YSZ were deposited by the axial suspension plasma spray process. Additionally, a triple layer TBC (GZdense/GZ/YSZ) comprising of denser GZ coating on top of GZ/YSZ TBC was deposited. SEM analysis revealed a columnar microstructure in the single, double and triple layer TBCs. XRD analysis confirmed the presence of tetragonal prime and defect fluorite phases in the top surface of YSZ and GZ based as sprayed TBCs respectively. The single layer YSZ and GZ/YSZ multi-layered TBCs were subjected to thermal cyclic fatigue (TCF) testing at 1100 °C and 1200 °C. The triple layer TBC showed a higher thermal cyclic life at both the temperatures compared to the single and double layer TBCs. The failed TBCs at 1100 °C were analyzed by SEM/EDS and image analysis. It was found that the failure modes in single layer YSZ and GZ based TBCs were different.

  • 334.
    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.

  • 335.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AGAlthofenAustria.
    Björklund, Stefan
    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.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Vaßen, Robert
    Institute of Energy and Climate Research (IEK-1) Forschungszentrum Jülich GmbHJülich Germany.
    Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1-2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM.

  • 336.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Jonnalagadda, Krishna Praveen
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Markocsan, Nicolaie
    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.
    Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 357, p. 456-465Article in journal (Refereed)
    Abstract [en]

    In this work, three double layered thermal barrier coating (TBC) variations with different gadolinium zirconate (GZ) and YSZ thickness (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400YSZ respectively, where the prefixed numbers before GZ and YSZ represent the layer thickness in μm), were produced by suspension plasma spray (SPS) process. The objective was to investigate the influence of YSZ thickness on the thermal conductivity and thermal shock lifetime of the GZ/YSZ double layered TBCs. The as sprayed TBCs were characterized using SEM, XRD and porosity measurements. Thermal diffusivity measurements were made using laser flash analysis and the thermal conductivity of the TBCs was calculated. The double layered TBC with the lowest YSZ (400GZ/100YSZ) thickness showed lower thermal diffusivity and thermal conductivity. The double layered TBCs were subjected to thermal shock test at a TBC surface temperature of 1350 °C. Results indicate that the TBC with a higher YSZ thickness (100GZ/400YSZ) showed inferior thermal shock lifetime whereas the TBCs with low YSZ thickness showed comparatively higher thermal shock lifetimes. Failure of the TBCs after thermal shock test was analyzed using SEM and XRD to gain further insights.

  • 337.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Jonnalagadda, Krishna Praveen
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Björklund, Stefan
    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.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Engineered architectures of gadolinium zirconate based thermal barrier coatings subjected to hot corrosion test2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 328, p. 361-370Article in journal (Refereed)
    Abstract [en]

    Abstract Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature TBC applications. Suspension plasma spray has shown the capability to generate a wide range of microstructures including the desirable columnar microstructure. In this study, two different TBC architectures were deposited using the axial suspension plasma spray. The first variation was a triple layered TBC comprising of thin YSZ base layer beneath a relatively porous GZ intermediate layer and a dense GZ top layer. The second variation was a composite TBC architecture of GZ and YSZ comprising of thin YSZ base layer and GZ + YSZ top layer. Cross sectional SEM analysis of the layered and composite TBCs revealed a columnar microstructure. The porosity content of the deposited TBCs was measured using two methods (Image Analysis and Water Intrusion). The as-sprayed TBCs were exposed at 900 °C for 8 h to a corrosive salt environment consisting of a mixture of vanadium pentoxide and sodium sulfate. XRD analysis on the as-corroded TBCs top surface showed the presence of gadolinium vanadate in both the layered and the composite TBCs. SEM/EDS analysis of the top surface and the cross-section of the layered and composite TBCs after hot corrosion test revealed the infiltration of the molten salts through the columnar gaps. The composite TBC showed a lower hot corrosion induced damage compared to the layered TBC where a considerable spallation was observed.

  • 338.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Ran
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Björklund, Stefan
    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.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Isothermal Oxidation Behavior of Gd2Zr2O7/YSZ Multilayered Thermal Barrier Coatings2016In: International Journal of Applied Ceramic Technology, ISSN 1546-542X, Vol. 13, no 3, p. 443-450Article in journal (Refereed)
    Abstract [en]

    Efficiency of a gas turbine can be increased by increasing the operating temperature. Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used in gas turbine applications. However, above 1200°C, YSZ undergoes significant sintering and CMAS (calcium magnesium alumino silicate) infiltration. New ceramic materials of rare earth zirconate composition such as gadolinium zirconate (GZ) are promising candidates for thermal barrier coating applications (TBC) above 1200°C. Suspension plasma spray of single-layer YSZ, double-layer GZ/YSZ, and a triple-layer TBC comprising denser GZ on top of GZ/YSZ TBC was attempted. The overall coating thickness in all three TBCs was kept the same. Isothermal oxidation performance of the three TBCs along with bare substrate and bond-coated substrate was investigated for time intervals of 10 h, 50 h, and 100 h at 1150°C in air environment. Weight gain/loss analysis was carried out by sensitive weighing balance. Microstructural analysis was carried out using scanning electron microscopy (SEM). As-sprayed single-layer YSZ and double-layer GZ/YSZ showed columnar microstructure, whereas the denser layer in the triple-layer TBC was not columnar. Phase analysis of the top surface of as-sprayed TBCs was carried out using XRD. Porosity measurements were made by water intrusion method. In the weight gain analysis and SEM analysis, multilayered TBCs showed lower weight gain and lower TGO thickness compared to single-layer YSZ.

  • 339.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ruelle, Céline
    ENSIL, Limoges, Franc.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Holmberg, Jonas
    Swerea IVF AB, Mölndal, Sweden.
    Björklund, Stefan
    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.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Understanding the effect of material composition and microstructural design on the erosion behavior of plasma sprayed thermal barrier coatings2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 488, p. 170-184Article in journal (Refereed)
    Abstract [en]

    In this work, three different TBC compositions comprising of yttria partially stabilized zirconia (8YSZ), yttria fully stabilized zirconia (48YSZ) and gadolinium zirconate (GZ) respectively, were processed by suspension plasma spray (SPS) to obtain columnar microstructured TBCs. Additionally, for comparison, lamellar microstructured, 7YSZ TBC was deposited by air plasma spray (APS) process. SEM analysis was carried out to investigate the microstructure and white light interferometry was used to evaluate the surface morphology of the as-sprayed TBCs. Porosity measurements were made using water intrusion and image analysis methods and it was observed that the SPS-YSZ and APS-YSZ TBCs showed higher porosity content than SPS-GZ and SPS-48YSZ. The as-sprayed TBC variations (APS-YSZ, SPS-YSZ, SPS-GZ, and SPS-48YSZ) were subjected to erosion test. Results indicate that the erosion resistance of APS-YSZ TBC was inferior to the SPS-YSZ, SPS-GZ and SPS-48YSZ TBCs respectively. Among the SPS processed TBCs, SPS-YSZ showed the highest erosion resistance whereas the SPS-48YSZ showed the lowest erosion resistance. SEM analysis of the eroded TBCs (cross section and surface morphology) was performed to gain further insights on their erosion behavior. Based on the erosion results and post erosion SEM analysis, erosion mechanisms for splat like microstructured APS TBC and columnar microstructured SPS TBCs were proposed. The findings from this work provide new insights on the erosion mechanisms of columnar microstructured TBCs and lamellar microstructured TBCs deposited by plasma spray. © 2019 Elsevier B.V.

  • 340.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zhou, Dapeng
    Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Germany.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Markocsan, Nicolaie
    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.
    Vassen, Robert
    Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Germany.
    Tailored microstructures of gadolinium zirconate/YSZ multi-layered thermal barrier coatings produced by suspension plasma spray: Durability and erosion testing2019In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 264, p. 283-294Article in journal (Refereed)
    Abstract [en]

    This work employed an axial suspension plasma spray (SPS) process to deposit two different gadolinium zirconate (GZ) based triple layered thermal barrier coatings (TBCs). The first was a 'layered' TBC (GZ dense/GZ/YSZ) where the base layer was YSZ, intermediate layer was a relatively porous GZ and the top layer was a relatively dense GZ. The second triple layered TBC was a 'composite' TBC (GZ dense/GZ + YSZ/YSZ) comprising of an YSZ base layer, a GZ + YSZ intermediate layer and a dense GZ top layer. The as sprayed TBCs (layered and composite) were characterized using SEM/EDS and XRD. Two different methods (water intrusion and image analysis) were used to measure the porosity content of the as sprayed TBCs. Fracture toughness measurements were made on the intermediate layers (GZ + YSZ layer of the composite TBC and porous GZ layer of the layered TBC respectively) using micro indentation tests. The GZ + YSZ layer in the composite TBC was shown to have a slightly higher fracture toughness than the relatively porous GZ layer in the layered TBC. Erosion performance of the as sprayed TBCs was evaluated at room temperature where the composite TBC showed higher erosion resistance than the layered TBC. However, in the burner rig test conducted at 1400 °C, the layered TBC showed higher thermal cyclic lifetime than the composite TBC. Failure analysis of the thermally cycled and eroded TBCs was performed using SEM and XRD. © 2018 Elsevier B.V.

  • 341.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zhou, Dapeng
    Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Germany.
    Vassen, Robert
    Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Germany.
    Effect of spray parameters on the microstructure and porosity content of gadolinium zirconate TBCs deposited by suspension plasma spray2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc , 2017, p. 31-35, article id DVS336Conference paper (Refereed)
    Abstract [en]

    Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature(>1200°C) thermal barrier coating (TBC) applications. Suspension plasma spray (SPS) technique has shown the capability to generate a wide range of microstructures which includes the more desirable columnar microstructure. In this study, GZ single layer TBCs were deposited by axial SPS process. The variable parameters include the standoff distance, solid load content of the suspension and input power. The cross section and top surface of the as sprayed TBCs were analyzed by SEM. The phase content in the as sprayed TBCs was analyzed by XRD. The porosity content of the as sprayed TBCs was measured using image analysis. In the SEM analysis, it was observed that a lower solid load content in the suspension favoured the formation of a columnar microstructure. Additionally, at lower solid load content, increase in standoff distance resulted in columnar microstructure with high porosity content in the TBC. However,with higher solid content suspension and alteration of input power, only adense vertical cracked microstructure can be obtained.                 

  • 342.
    Maimaitiyili, Tuerdi
    et al.
    Photons for Engineering and Manufacturing Group, Paul Scherrer Institute, 5232 Villigen, Switzerland ; Malmö universitet, Department of Materials Science and Applied Mathematics, 20506 Malmö, Sweden.
    Woracek, Robin
    European Spallation Source ERIC, 22100 Lund, Sweden ; Nuclear Physics Institute of the CAS, 250 68 Husinec—Rež, Czech Republic.
    Neikter, Magnus
    Luleå University of Technology, Division of Materials Science, 971 81 Luleå, Swed.
    Boin, Mirko
    Department of Microstructure and Residual Stress Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
    Wimpory, Robert C.
    Department of Microstructure and Residual Stress Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
    Pederson, Robert
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Strobl, Markus
    European Spallation Source ERIC, 22100 Lund, Sweden ; Nuclear Physics Institute of the CAS, 250 68 Husinec—Rež, Czech Republic ;Neutron Imaging and Applied Materials Group, Paul Scherrer Institute, 5232 Villigen, Switzerland .
    Drakopoulos, Michael
    maging and Microscopy Group, Diamond Light Source Ltd., Oxfordshire OX11 0DE, U.
    Schäfer, Norbert
    Department of Nanoscale Structures and Microscopic Analysis, Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany.
    Bjerkén, Christina
    Malmö universitet, Department of Materials Science and Applied Mathematics, 20506 Malmö, Sweden.
    Residual Lattice Strain and Phase Distribution in Ti-6Al-4V Produced by Electron Beam Melting2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 4, article id 667Article in journal (Refereed)
    Abstract [en]

    Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.

  • 343.
    Majid, Farajian
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Järvstråt, Niklas
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    A imperfect fractographical investigation of weld toe ions in Tandem GMA welding2006In: Steel Research International, ISSN 1611-3683, Vol. 77, no 12, p. 889-895Article in journal (Refereed)
  • 344.
    Mandati, Sreekanth
    et al.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur P. O., Hyderabad, Telangana 500005, India; Department of Materials Science and Metallurgical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502285, India .
    Dey, Suhash R.
    Department of Materials Science and Metallurgical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502285, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Bulusu, Sarada. V.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur P. O., Hyderabad, Telangana 500005, India.
    Cu(In,Ga)Se2 Films with Branched Nanorod Architectures Fabricated by Economic and Environmentally Friendly Pulse-Reverse Electrodeposition Route2018In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 6, no 11, p. 13787-13796Article in journal (Refereed)
    Abstract [en]

    Cu(In,Ga)Se2 (CIGS) materials are one of the most promising solar cell technologies owing to their large absorption coefficient and tunable direct bandgap, and they have gained considerable commercial maturity. The study herein puts forward the preparation of nanostructured CIGS films containing branched nanorod architectures, which is reported for the first time. The process employs an economic pulse-reverse electrodeposition technique by utilizing the fundamentals of electro-reduction and oxidation to fabricate nanostructured CIGS and completely avoids conventional energy-intensive high-temperature annealing/selenization step. Comprehensive characterization of nanoarchitectured films reveals the stoichiometric composition and chalcopyrite structure with dominant (112) orientation. Nanostructured CIGS exhibits excellent photoactivity with a photocurrent density of 4.31 mA/cm2 at -0.13 V vs RHE in a liquid junction, which is highest for a bare CIGS film and is attributable to its inherent high interface area and better charge transport properties compared to planar films. The ability to produce such efficient nanostructures using an economic, scalable, sustainable, and eco-friendly approach can considerably reduce fabrication costs compared with existing high-temperature bulk material preparation methods. © 2018 American Chemical Society.

  • 345.
    Manitsas, Dimosthenis
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Hot Cracking Mechanisms in Welding Metallurgy: A Review of Theoretical Approaches2018In: MATEC Web of conferences, E-ISSN 2261-236X, Vol. 188, article id 03018Article in journal (Refereed)
    Abstract [en]

    Hot cracking often refers to the appearance of liquid films along grain boundaries or to another place in the weld metal structure. Despite hot cracking importance in alloy weldability, there is limited understanding of the influencing mechanisms. Theories and criteria worked out over the years to assess alloy weldability will be presented. The review focuses on: 1) Theories of hot cracking, 2) Hot cracking criteria, and 3) A criticism of hot cracking theories and criteria.

  • 346.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Functional coatings for high temperature applications in transport and energy sectors2016Conference paper (Other (popular science, discussion, etc.))
  • 347.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    High-performance TBCs by SPS2016Conference paper (Other academic)
  • 348.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Influence of Coating Morphology on Thermal Properties and Thermal Cyclic Lifetime of Axial Suspension Plasma Sprayed Thermal Barrier Coatings2015Conference paper (Other academic)
  • 349.
    Markocsan, Nicolaie
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    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.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång, Sweden.
    Wigren, Jan
    GKN Aerospace,Trollhättan,Sweden.
    Liquid Feedstock Plasma Spraying: An Emerging Process for Advanced Thermal Barrier Coatings2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 6, p. 1104-1114Article in journal (Refereed)
    Abstract [en]

    Liquid feedstock plasma spraying (LFPS) involves deposition of ultrafine droplets of suspensions or solution precursors (typically ranging from nano- to submicron size) and permits production of coatings with unique microstructures that are promising for advanced thermal barrier coating (TBC) applications. This paper reviews the recent progress arising from efforts devoted to development of high-performance TBCs using the LFPS approach. Advancements in both suspension plasma spraying and solution precursor plasma spraying, which constitute the two main variants of LFPS, are presented. Results illustrating the different types of the microstructures that can be realized in LFPS through appropriate process parameter control, model-assisted assessment of influence of coating defects on thermo-mechanical properties and the complex interplay between pore coarsening, sintering and crystallite growth in governing thermal conductivity are summarized. The enhancement in functional performances/lifetime possible in LFPS TBCs with multilayered architectures and by incorporating new pyrochlore chemistries such as gadolinium zirconate, besides the conventional single 8 wt.% yttria-stabilized zirconia insulating ceramic layer, is specifically highlighted.

  • 350.
    Markocsan, Nicolaie
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylen, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wigren, J.
    Li, X-H
    Liquid feedstock plasma spraying: an emerging processfor the next generation aircraft engines2016Conference paper (Other academic)
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