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  • 51.
    Goel, Sneha
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ahlfors, Magnus
    Quintus Technologies AB, Västerås, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    The Effect of Location and Post-treatment on the Microstructure of EBM-Built Alloy 7182018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, p. 115-129Conference paper (Refereed)
    Abstract [en]

    Additive manufacturing (AM) of Ni-based superalloys such as Alloy 718 may obviate the need for difficult machining and welding operations associated with geometrically intricate parts, thus potentially expanding design possibilities and facilitating cost-effective manufacture of complex components. However, processing AM builds completely free from defects, which may impair mechanical properties such as fatigue and ductility, is challenging. Anisotropic properties, microstructural heterogeneities and local formation of undesired phases are additional concerns that have motivated post-treatment of AM builds. This work investigates the microstructural changes associated with post-treatment of Alloy 718 specimens produced by Electron Beam Melting (EBM) for as-built microstructures at 3 build heights: near base plate, in the middle of build and near the top of the build. Two different post-treatment conditions, hot isostatic pressing (HIP) alone and a combined HIP with solutionising and two-step aging were examined and compared to the results for the as-built condition. The influence of various post-treatments on minor phase distributions (δ, γ″, carbides), overall porosity, longitudinal grain widths and Vickers microhardness was considered. The HIP treatment led to significant reduction in overall porosity and dissolution of δ phase, which led to appreciable grain growth for both post-treatment conditions. The variation in hardness noted as a function of build height for the as-built specimens was eliminated after post-treatment. Overall, the hardness was found to decrease after HIP and increase after the full HIP, solutionising and aging treatment, which was attributed to dissolution of γ″ during HIP and its re-precipitation in subsequent heat treatment steps.

  • 52.
    Gruber, H.
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Division of Materials and Manufacture, Gothenburg, SE-412 96, Sweden.
    Karimi Neghlani, Paria
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hryha, E.
    Chalmers University of Technology, Department of Industrial and Materials Science, Division of Materials and Manufacture, Gothenburg, SE-412 96, Sweden.
    Nyborg, L.
    Chalmers University of Technology, Department of Industrial and Materials Science, Division of Materials and Manufacture, Gothenburg, SE-412 96, Sweden.
    Effect of Powder Recycling on the Fracture Behavior of Electron Beam Melted Alloy 7182018In: Powder Metallurgy Progress, ISSN 1335-8987, Vol. 18, no 1, p. 40-48Article in journal (Other academic)
    Abstract [en]

    Understanding the effect of powder feedstock alterations during multicycle additive manufacturing on the quality of built components is crucial to meet the requirements on critical parts for aerospace engine applications. In this study, powder recycling of Alloy 718 during electron beam melting was studied to understand its influence on fracture behavior of Charpy impact test bars. High resolution scanning electron microscopy was employed for fracture surface analysis on test bars produced from virgin and recycled powder. For all investigated samples, an intergranular type of fracture, initiated by non-metallic phases and bonding defects, was typically observed in the regions close to or within the contour zone. The fracture mode in the bulk of the samples was mainly moderately ductile dimple fracture. The results show a clear correlation between powder degradation during multi-cycle powder reuse and the amount of damage relevant defects observed on the fracture surfaces. In particular, samples produced from recycled powder show a significant amount of aluminum-rich oxide defects, originating from aluminum-rich oxide particulates on the surface of the recycled powder. © 2018 H. Gruber et al., published by Sciendo.

  • 53.
    Guerin, Elie
    et al.
    National School of Engineers, University of Limoges, Limoges, France.
    Sadeghimeresht, Esmaeil
    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.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Role of Chemistry on Corrosion Behavior of Various Ni-based HVAF-Sprayed Coatings in Simulated Boiler Environments2017Conference paper (Other academic)
  • 54.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Design of Thermal Barrier Coatings: A Modelling Approach2015Book (Other academic)
    Abstract [en]

    This book details the relationships between microstructure, interface roughness, and properties of thermal barrier coatings. The author proposes a method for the reduction of the thermal conductivity of the ceramic layer in order to increase the lifetime of thermal barrier coatings. He includes models for the optimization of ceramic layer microstructure and interface roughness.

  • 55.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Spraying of solid oxide fuel cells2016Conference paper (Other academic)
  • 56.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eriksson, Robert
    Linköping University, Linköping, Sweden.
    Sand, Ulf
    EDR Medeso, Västerås, Sweden.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    A Diffusion-based Oxide Layer Growth Model using Real Interface Roughness in Thermal Barrier Coatings for Lifetime Assessment2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 271, no June, p. 181-191Article in journal (Refereed)
    Abstract [en]

    The development of thermo-mechanical stresses during thermal cycling can lead to the formation of detrimental cracks in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings systems (TBCs). These stresses are significantly increased by the formation of a Thermally Grown Oxide (TGO) layer that forms through the oxidation of mainly aluminium in the bondcoat layer of the TBC. As shown in previous work done by the authors, the topcoat-bondcoat interface roughness plays a major role in the development of the stress profile in the topcoat and significantly affects the lifetime of TBCs. This roughness profile varies as the TGO layer grows and changes the stress profile in the topcoat leading to crack propagation and thus failure.

    In this work, a two-dimensional TGO growth model is presented, based on oxygen and aluminium diffusion-reaction equations, using real interface profiles extracted from cross-section micrographs. The model was first validated by comparing the TGO profiles artificially created by the model to thermally cycled specimens with varying interface roughness. Thereafter, stress profiles in the TBC system, before and after the TGO layer growth, were estimated using a finite element modelling model described in previous work done by the authors. Three experimental specimens consisting of the same chemistry but with different topcoat-bondcoat interface roughness were studied by the models and the stress state was compared to the lifetimes measured experimentally. The combination of the two models described in this work was shown to be an effective approach to assess the stress behaviour and lifetime of TBCs in a comparative way.

  • 57.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Kuhn, J.
    Kesler, O.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Influence of Process Parameters on Microstructure and Permeability of Axial Suspension Plasma Sprayed Electrolytes in SOFCs2016Conference paper (Other academic)
  • 58.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Kumara, Chamara
    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.
    Bilayer Suspension Plasma-Sprayed Thermal Barrier Coatings with Enhanced Thermal Cyclic Lifetime: Experiments and Modeling2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 6, p. 1038-1051Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying (SPS) has been shown as a promising process to produce porous columnar strain tolerant coatings for thermal barrier coatings (TBCs) in gas turbine engines. However, the highly porous structure is vulnerable to crack propagation, especially near the topcoat-bondcoat interface where high stresses are generated due to thermal cycling. A topcoat layer with high toughness near the topcoat-bondcoat interface could be beneficial to enhance thermal cyclic lifetime of SPS TBCs. In this work, a bilayer coating system consisting of first a dense layer near the topcoat-bondcoat interface followed by a porous columnar layer was fabricated by SPS using Yttria-stabilised zirconia suspension. The objective of this work was to investigate if the bilayer topcoat architecture could enhance the thermal cyclic lifetime of SPS TBCs through experiments and to understand the effect of the column gaps/vertical cracks and the dense layer on the generated stresses in the TBC during thermal cyclic loading through finite element modeling. The experimental results show that the bilayer TBC had significantly higher lifetime than the single-layer TBC. The modeling results show that the dense layer and vertical cracks are beneficial as they reduce the thermally induced stresses which thus increase the lifetime.

  • 59.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, X. -H
    Siemens Turbomachinery, Finspång, Sweden.
    Kjellman, B.
    GKN Aerospace, Trollhättan, Sweden.
    Influence of bondcoat surface characteristics on lifetime in suspension plasma sprayed thermal barrier coatings2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc , 2017, Vol. 2, p. 883-887Conference paper (Refereed)
    Abstract [en]

    Development of TBCs allowing higher combustion temperatures in gas turbines is of high commercial interest since it results in higher fuel efficiency and lower emissions. It is well known that TBCs produced by suspension plasma spraying (SPS) have lower thermal conductivity as compared to conventional systems due to their very fine porous microstructure. Moreover, columnar structured SPS TBCs are significantly cheaper to produce as compared to the conventionally used electron beam - physical vapour deposition (EB-PVD). However, SPS TBCs have not yet been commercialised due to low reliability and life expectancy of the coatings. Lifetime of a TBC system is significantly dependent on topcoat-bondcoat interface topography. The objective of this work was to study the effect of topcoat-bondcoat interface in SPS TBCs by changing bondcoat spray parameters and bondcoat surface heat treatment High velocity air fuel (HVAF) spraying was used for bondcoat deposition while axial-SPS was used for topcoat deposition. Same topcoat spray parameters were used for all samples. Lifetime was examined by thermal cyclic fatigue and thermal shock testing. The influence of surface roughness on lifetime has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition to achieve long lifetime SPS TBCs. 

  • 60.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, X. -H
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Östergren, Lars
    GKN Aerospace, Trollhättan, Sweden.
    Influence of Bondcoat Spray Process on Lifetime of Suspension Plasma-Sprayed Thermal Barrier Coatings2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 1-2, p. 84-97Article in journal (Refereed)
    Abstract [en]

    Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable of producing highly porous columnar microstructures similar to the conventionally used electron beam–physical vapor deposition. However, lifetime of SPS coatings needs to be improved further to be used in commercial applications. The bondcoat microstructure as well as topcoat–bondcoat interface topography affects the TBC lifetime significantly. The objective of this work was to investigate the influence of different bondcoat deposition processes for SPS topcoats. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial vacuum plasma-sprayed NiCoCrAlY and PtAl diffusion bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study bondcoat oxidation over time. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

  • 61.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, X.
    Kjellman, B.
    Effect of bondcoat and substrate chemistry on oxide growth and lifetime in suspension plasma sprayed thermal barrier coatings2017Conference paper (Other academic)
  • 62.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, X-H
    Influence of topcoat-bondcoat interface on lifetime in suspension sprayed therma barrier coatings2016Conference paper (Other academic)
  • 63.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Turbomachinery AB, Finspång, Sweden.
    Kjellman, Björn
    GKN Aerospace, Trollhättan, Sweden.
    Development of bondcoats for high lifetime suspension plasma sprayed thermal barrier coatings2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347Article in journal (Refereed)
    Abstract [en]

    Fabrication of thermal barrier coatings (TBCs) by suspension plasma spraying (SPS) seems to be a promising alternative for the industry as SPS TBCs have the potential to provide lower thermal conductivity and longer lifetime than state-of-the-art allowing higher engine efficiency. Further improvements in lifetime of SPS TBCs and fundamental understanding of failure mechanisms in SPS TBCs are necessary for their widespread commercialisation. In this study, the influence of varying topcoat-bondcoat interface topography and bondcoat microstructure on lifetime was investigated. The objective of this work was to gain fundamental understanding of relationships between topcoat-bondcoat interface topography, bondcoat microstructure, and failure mechanisms in SPS TBCs. Seven sets of samples were produced in this study by keeping same bondcoat chemistry but varying feedstock particle size distributions and bondcoat spray processes. The topcoat chemistry and spray parameters were kept identical in all samples. Three-dimensional surface measurements along with scanning electron microscopy images were used to characterise bondcoat surface topography. The effect of varying interface topography and bondcoat microstructure on thermally grown oxide formation, stresses and lifetime was discussed. The results showed that varying bondcoat powder size distribution and spray process can have a significant effect on lifetime of SPS TBCs. Smoother bondcoats seemed to enhance the lifetime in case of SPS TBCs in case of same bondcoat chemistry and similar bondcoat microstructures. When considering the samples investigated in this study, samples with high velocity air-fuel (HVAF) bondcoats resulted in higher lifetime than other samples indicating that HVAF could be a suitable process for bondcoat deposition in SPS TBCs. © 2018 Elsevier B.V.

  • 64.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Peng, Ru Lin
    Linköping University, Linköping, Sweden.
    Improving the lifetime of suspension plasma sprayed thermal barrier coatings2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 550-559Article in journal (Refereed)
    Abstract [en]

    Development of thermal barrier coating systems (TBCs) for gas turbine applications allowing higher combustion temperatures is of high interest since it results in higher fuel efficiency and lower emissions. TBCs produced by suspension plasma spraying (SPS) have been shown to exhibit significantly lower thermal conductivity as compared to conventional systems due to their very fine porosity microstructure. However they have not been commercialised yet due to low reliability and life expectancy of the coatings. In addition to the initial topcoat microstructure and its sintering resistance, lifetime of a TBC system is highly dependent on bondcoat chemistry as it influences the growth rate of thermally grown oxide (TGO) layer. To enhance the lifetime of SPS TBCs, fundamental understanding of relationships between topcoat microstructure and its evolution with time, bondcoat chemistry, TGO growth rate, and lifetime is essential. The objective of this work was to study the effect of topcoat microstructure evolution and TGO growth rate on lifetime in SPS TBC systems. Experimental MCrAlY bondcoat powders with different aluminium activities were investigated and compared to a commercial bondcoat powder. High velocity air fuel spraying was used for bondcoat deposition while axial-SPS was used for yttria stabilized zirconia topcoat deposition. Lifetime was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study TGO evolution with time. The changes in microstructure of SPS coatings due to sintering under long term exposure at high temperatures were investigated. Different failure modes in SPS TBCs were also examined. The bondcoat with higher aluminium activity resulted in a significantly higher thermal cyclic lifetime of the corresponding TBC as it could have promoted protective alumina layer growth for a longer period of time. The results indicate that the significant changes in topcoat microstructure due to sintering as observed in this work could have a detrimental effect on TBC lifetime. © 2017 Elsevier B.V.

  • 65.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång, Sweden.
    Östergren, Lars
    GKN Aerospace, Trollhättan, Sweden.
    Development of bondcoat layer for long lifetime suspension plasma sprayed thermal barrier coatings2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc , 2017, Vol. 2, p. 1158-1163Conference paper (Refereed)
    Abstract [en]

    Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable to produce columnar microstructures similar to the conventionally used electron beam – physical vapour deposition (EB-PVD) process. Moreover, SPS is a significantly cheaper process and can also produce more porous coatings than EB-PVD. However, lifetime of SPS coatings needs to be improved further for them to be applicable in commercial applications.The bondcoat microstructure as well as topcoat-bondcoat interface topography affect the TBC lifetime significantly. The objective of this work was to investigate the feasibility of different bondcoat deposition process for SPS TBCs. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial NiCoCrAlY and PtAl bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

  • 66.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Rocchio-Heller, R.
    Oerlikon Metco, Westbury, USA.
    Liu, J.
    Oerlikon Metco, Westbury, USA.
    Li, X. -H
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Östergren, L.
    GKN Aerospace, Trollhättan, Sweden.
    Failure Analysis of Multilayered Suspension Plasma-Sprayed Thermal Barrier Coatings for Gas Turbine Applications2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 402-411-Article in journal (Refereed)
    Abstract [en]

    Improvement in the performance of thermal barrier coatings (TBCs) is one of the key objectives for further development of gas turbine applications. The material most commonly used as TBC topcoat is yttria-stabilized zirconia (YSZ). However, the usage of YSZ is limited by the operating temperature range which in turn restricts the engine efficiency. Materials such as pyrochlores, perovskites, rare earth garnets are suitable candidates which could replace YSZ as they exhibit lower thermal conductivity and higher phase stability at elevated temperatures. The objective of this work was to investigate different multilayered TBCs consisting of advanced topcoat materials fabricated by suspension plasma spraying (SPS). The investigated topcoat materials were YSZ, dysprosia-stabilized zirconia, gadolinium zirconate, and ceria–yttria-stabilized zirconia. All topcoats were deposited by TriplexPro-210TM plasma spray gun and radial injection of suspension. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. Microstructure analysis of as-sprayed and failed specimens was performed with scanning electron microscope. The failure mechanisms in each case have been discussed in this article. The results show that SPS could be a promising route to produce multilayered TBCs for high-temperature applications.

  • 67.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Rocchio-Heller, Riston
    Oerlikon Metco, Westbury, USA.
    Liu, Jing
    Oerlikon Metco, Westbury, USA.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Fingspång, Sweden.
    Östergren, Lars
    GKN Aerospace, Trollhättan, Sweden.
    Multilayered suspension plasma sprayed thermal barrier coatings for high temperature gas turbine applications2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc , 2017, p. 382-387Conference paper (Refereed)
    Abstract [en]

    Improvement in the performance of thermal barrier coating systems (TBCs) is one of the key objectives for further development of gas turbine applications. The material most commonly used as TBC topcoat is yttria stabilised zirconia (YSZ). However, the usage of YSZ is limited by the operating temperature range which in turn restricts the engine efficiency. Materials such as pyrochlores, perovskites, rare earth garnets, etc. are suitable candidates which could replace YSZ as they exhibit lower thermal conductivity and higher phase stability at elevated temperatures.The objective of this work was to investigate different multi-layered TBCs consisting of advanced topcoat materials fabricated by Suspension Plasma Spraying (SPS). The investigated topcoat materials were YSZ, dysprosia stabilised zirconia, gadolinium zirconiate, cerium doped YSZ and yttria fully stabilised zirconia. All topcoats were deposited with TriplexPro-210 plasma spray gun and radial injection of suspension. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. Microstructure analysis of as-sprayed and failed specimens was performed with scanning electron microscope. The failure mechanisms in each case have been discussed in this article. The results show that SPS could be a promising route to produce multilayered TBCs for high temperature applications.

  • 68.
    Gupta, Mohit Kumar
    et al.
    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.
    Design of Low Thermal Conductivity Thermal Barrier Coatings by Finite Element Modelling2011In: Surface Modification Technologies XXIV: SMT24, Dresden, September 7-9, 2010 / [ed] T. S. Sudarshan, Eckhard Beyer, and Lutz-Michael Berger, 2011, p. 353-365Conference 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 (TBC). Object Oriented Finite element analysis (OOF) has recently been shown as an effective tool for evaluating thermo-mechanical material behaviour as this method is capable of incorporating the inherent material microstructure as an input to the model. The objective of this work was to evaluate a procedure where this technique is combined with Tbctool, a plasma-sprayed TBC like morphology generator, thus enabling development of low thermal conductivity coatings by simulation. Input parameters for Tbctool were computed from SEM images of sprayed microstructures using the image analysis software, Aphelion. Microstructures for as-sprayed as well as heat treated samples were evaluated. The thermal conductivities of the artificially generated microstructures were determined using OOF. Verification of the modelling procedure was performed by comparing predicted values by OOF with corresponding measured values using the laser flash technique. The results, although tentative in nature, indicate that the proposed simulation approach can be a powerful tool in the development of new low conductivity coatings.

  • 69.
    Gupta, Mohit Kumar
    et al.
    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.
    Structure-property Relationships in Thermal Barrier Coatings by Finite Element Modelling2012In: Surface Modification Technologies XXV : proceedings of the Twenty Fifth International Conference on Surface Modification Technologies: SMT25, Trollhättan, June 20-22, 2011 / [ed] T. S. Sudarshan, and P. Nylén, [Chennai]: Valardocs , 2012, p. 175-184Conference paper (Refereed)
    Abstract [en]

    The thermal and mechanical properties of Thermal Barrier Coating systems (TBCs) are strongly influenced by coating defects, such as delaminations and pores, thus making it essential to have a fundamental understanding of microstructure-property relationships in TBCs, to produce a desired coating. Object-Oriented Finite element analysis (OOF) has been shown previously as an effective tool for evaluating thermal and mechanical material behaviour, as this method is capable of incorporating the inherent material microstructure as an input to the model. In this work, OOF was used to predict the thermal conductivity and effective Young’s modulus of TBC topcoats. A Design of Experiments (DoE) was conducted by varying selected spray parameters for spraying Yttria Partially Stabilized Zirconia (YPSZ) topcoat. Characterisation of the coatings included microstructure, porosity and crack content and thermal conductivity measurements. The relationships between microstructural features, thermal conductivity and Young’s modulus are discussed.

  • 70.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Skogsberg, Kristoffer
    University West, Department of Engineering Science.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of topcoat-bondcoat interface roughness on stresses and lifetime in Thermal Barrier Coatings2013In: Proceedings of the International Thermal Spray Conference / [ed] Editor: Rogerio S. Lima, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Georg Mauer, André McDonald, and Filofteia-Laura, ASM International, 2013, p. 596-601Conference paper (Refereed)
    Abstract [en]

    Failure in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) is associated with the thermomechanical stresses developing due to the Thermally Grown Oxide (TGO) layer growth and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs. Modeling has been shown as an effective tool to understand the effect of interface roughness on induced stresses. In previous work done by the research group, it was observed that APS bondcoats performed better than the bondcoats sprayed with High Velocity OxyFuel (HVOF) process which is contrary to the present literature data. The objective of this work was to understand this observed difference in life-time with the help of finite element modeling by using real surface topographies. Different TGO layer thicknesses were evaluated. The modeling results were also compared with existing theories established on simplified sinusoidal profiles published in earlier works. It was shown that modeling can be used as an effective tool to understand the stress behavior in TBCs with different roughness profiles.

  • 71.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Skogsberg, Kristoffer
    University West, Department of Engineering Science.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of Topcoat-Bondcoat Interface Roughness on Stresses and Lifetime inThermal Barrier Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 1-2, p. 170-181Article in journal (Refereed)
    Abstract [en]

    Failure in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) is associated with the thermo-mechanical stresses developing due to the Thermally Grown Oxide (TGO) layer growth and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs. Modeling has been shown as an effective tool to understand the effect of interface roughness on induced stresses. In previous work done by our research group, it was observed that APS bondcoats performed better than the bondcoats sprayed with High Velocity Oxy-Fuel (HVOF) process which is contrary to the present literature data. The objective of this work was to understand this observed difference in lifetime with the help of finite element modeling by using real surface topographies. Different TGO layer thicknesses were evaluated. The modeling results were also compared with existing theories established on simplified sinusoidal profiles published in earlier works. It was shown that modeling can be used as an effective tool to understand the stress behavior in TBCs with different roughness profiles.

  • 72.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Weber, André
    Karlsruhe Institute of Technology, Germany.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gindrat, Malko
    Oerlikon Metco, Switzerland.
    Electrochemical Performance of Plasma Sprayed Metal Supported Planar Solid Oxide Fuel Cells2016In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 9, p. F1059-F1065Article in journal (Refereed)
    Abstract [en]

    High production cost is one of the major barriers to widespread commercialization of solid oxide fuel cells (SOFCs). Thermal spraytechniques are a low cost alternative for the production of SOFCs. The objective of this work was to evaluate the electrochemicalperformance of cells produced by plasma spraying. The anode was deposited on a porous metallic support by atmospheric plasmaspraying (APS) whereas the electrolyte was deposited by plasma spray-thin film (PS-TF) technique, which can produce thin anddense coatings at high deposition rates. The cathode was deposited by screen-printing and in-operando sintering. The electrochemicaltests were performed at 650–800◦C. Current-voltage characteristics and impedance spectra were measured and analyzed. The impactof electrolyte composition and layer thickness on the gas tightness of the electrolyte and the area specific resistance of the cell isdiscussed. The results show that the applied thermal spraying techniques are a potential alternative for producing SOFCs.

  • 73.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Weber, André
    Karlsruhe Institute of Technology, Germany.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Helden, Nadine
    Oerlikon Metco, Germany.
    Development of plasma sprayed Ni/YSZ anodes for metal supported solidoxide fuel cells2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 178-189Article in journal (Refereed)
    Abstract [en]

    Solid oxide fuel cells (SOFCs) offer a promising technique for producing electricity by clean energy conversionthrough an electrochemical reaction of fuel and air. Plasma spraying could be a potential manufacturing routefor commercial SOFCs, as it provides a distinct advantage especially in case of metal supported cells (MSCs) byallowing rapid processing at relatively low processing temperatures preventing thus the degradation of themetallicsubstrate. The objective of this work was to develop nickel/yttria stabilised zirconia (Ni/YSZ) anodes withhigh porosity and homogeneous phase distribution by atmospheric plasma spraying forMSCs. Various feedstockmaterial approaches were explored in this study, both with single injection aswell as separate injection of differentfeedstock materials , and with and without the use of pore formers to create additional porosity. The advantagesand issues with each material route were investigated and discussed. It was shown that agglomerated Ni/YSZ/polyester feedstock material resulted in the best distribution of Ni and YSZ in the anodemicrostructurewithhomogeneous porosity. Subsequently, the Ni/YSZ/polyester material route with different amounts and size distributionsof polyester was chosen to develop anode symmetrical cells using a commercial zirconia sheet as supportfor electrochemical testing. The Ni/YSZ/polyester anode powder with 10 wt.% standard size polyesterexhibited the best electrochemical performance. The results show that plasma spraying of the agglomeratedNi/YSZ/polyester could be a promising route to achieve high performance and rapid production anodes withoutusing the carcinogenic nickel oxide.

  • 74.
    Gutnichenko, O
    et al.
    Division of Production and Materials Engineering, Lund University, Lund, S-22100, Sweden.
    Agic, Adnan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. SECO Tools AB, Björnbacksvägen 2, Fagersta, 73782, Sweden.
    Ståhl, J-E
    Division of Production and Materials Engineering, Lund University, Lund, S-22100, Sweden.
    Modeling of Force Build-up Process and Optimization of Tool Geometry when Intermittent Turning2017In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 393-398Article in journal (Refereed)
    Abstract [en]

    Intermittent turning the slotted workpieces is always accompanied with a high impact load of the machine tool during the entry phase of the cutting edge. The process leads to a strong dynamic response of the system and results in vibrations arose and potential tool life and surface finish issues. The present study addresses the modeling of cutting force build-up process with further optimization of cutting edge geometry where tooltip overshoot during the tool entry is selected as an objective function. The model takes into consideration the interaction between three units of the machine tool such as a tool, toolpost, and workpiece as well as an influence of the process on the system's dynamics.

  • 75.
    Hamatuli, Cliff
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Skräddad mikrostruktur av gadolinium zirkonat baserade värmebarriärbeläggningar som utsätts för termisk cyklisk utmattning2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Yttria Stabilized Zirconia (YSZ) is the standard ceramic top coat material used for TBC application. Above 1200°C, issues such as CMAS (Calcium Magnesium Alumino Silicates) infiltration susceptibility, phase instability and high sintering rates limits its long durability. Therefore, new materials which can overcome these challenges without compromising the other requirements for TBCs are highly desirable. Gadolinium zirconate is one such material which has shown promising results for CMAS infiltration resistance. In this work, a relatively new TBC processing route, suspension plasma spray (SPS) has been employed to deposit gadolinium zirconate based TBCs. The primary aim of this study was to deposit two different coating systems (layered and composite) of gadolinium zirconate and YSZ composition using SPS technique and evaluate their thermal cyclic fatigue life performance. The layered system was a triple layered TBC with YSZ as the base layer, relatively porous GZ as the intermediate layer and dense GZ as the top layer. The blended TBC system comprised of a thin YSZ layer, an intermediate GZ+YSZ thick layer and dense GZ top layer. In the thermal cyclic fatigue test at 1100°C and 1200°C, it was observed that blended TBC had a lower thermal cyclic life than the layered TBC. It was shown that SPS is a promising technique to deposit columnar microstructure TBCs. 

  • 76.
    Hameed, Pearlin
    et al.
    Centre for Biomaterials, Cellular & Molecular Theranostics (CBCMT), Vellore Institute of Technology, Vellore, 632014, India.
    Gopal, Vasanth
    Centre for Biomaterials, Cellular & Molecular Theranostics (CBCMT), Vellore Institute of Technology, Vellore, 632014, India; Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore, 632014, India.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ganvir, Ashish
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sen, Dwaipayan
    Centre for Biomaterials, Cellular & Molecular Theranostics (CBCMT), Vellore Institute of Technology, Vellore, 632014, India.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Manivasagam, Geetha
    Centre for Biomaterials, Cellular & Molecular Theranostics (CBCMT), Vellore Institute of Technology, Vellore, 632014, India.
    Axial Suspension Plasma Spraying: An ultimate technique to tailor Ti6Al4V surface with HAp for orthopaedic applications2019In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 173, p. 806-815Article in journal (Refereed)
    Abstract [en]

    Dissolution of atmospheric plasma sprayed (APS) hydroxyapatite (HAp) coatings on Ti-6Al-4 V medical implants have always been a challenge to overcome in the field of biomedical industry. In the present work, an attempt has been made to develop a HAp coating using a novel thermal spray process called axial suspension plasma spraying (SPS), which leads to thin adherent coatings. Two HAp coatings fabricated by APS (P1 and P2) and four SPS HAp coatings (S1, S2, S3 and S4) produced with varying spraying parameters were characterized in terms of (1) microstructure, porosity, hardness, adhesion strength, contact angle and phase purity; (2) corrosion resistance in 10% Fetal bovine serum (FBS); (3) in-vitro cell adherence and cell viability using human umbilical cord blood-derived mesenchymal stem cells (hMSCs). Amongst different APS and SPS coatings, P1 and S3 exhibited superior properties. S3 coating developed using SPS exhibited 1.3 times higher adhesion strength when compared to APS coating (P1) and 9.5 times higher corrosion resistance than P1. In addition, both S3 and P1 exhibited comparatively higher biocompatibility as evidenced by the presence of more than 92% viable hMSCs. © 2018 Elsevier B.V.

  • 77.
    Hoier, P.
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology,GothenburgSweden.
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology,GothenburgSweden.
    Tamil Alagan, Nageswaran
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, A.
    KN Aerospace Engine Systems AB,Trollhättan,Sweden.
    Characterization of tool wear when machining alloy 718 with high-pressure cooling using conventional and surface-modified WC-Co tools2017In: Journal of Superhard Materials, ISSN 1063-4576, Vol. 39, no 3, p. 178-185Article in journal (Refereed)
    Abstract [en]

    Coolant supplied by high pressure into the cutting zone has shown the lower thermal loads on the tool when machining difficult-to-cut materials as the Alloy 718. In this study, we investigate how the combination of high-pressure cooling and tool-surface modifications can lead to further improvements regarding tool life. The general approach is to enhance the coolant-tool interaction by increasing the contact area. Therefore, we machined cooling features into flank and rake faces of commercially available cemented tungsten carbide inserts. In this way, the surface area was increased by similar to 12%. After the cutting tests, the tools were analyzed by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Compared with conventional tools, the tool modifications reduced the flank wear by 45% for the investigated cutting parameters. Furthermore, we were able to significantly increase the cutting speed and feed rate without failure of the tool. The investigated surface modifications have great potential to enhance the productivity of metal cutting processes.

  • 78.
    Hoier, Philipp
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology, Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology, Gothenburg, Sweden.
    Tamil Alagan, Nageswaran
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Characterization of tool wear when machining Alloy 718 with high pressure cooling using conventional and surface-modified WC-Co tools2016In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Coolant supplied by high pressure into the cutting zone has shown to lower thermal loads on the tool when machining difficult-to-cut materials as Alloy 718. In this study, we investigate how the combination of high pressure cooling and tool-surface modifications can lead to further improvements regarding tool life. The general approach is to enhance the coolant-tool interaction by increasing the contact area. Therefore, we machined cooling features into flank and rake faces of commercially available cemented tungsten carbide inserts. In this way, the surface area was increased by ~ 12%. After the cutting tests, the tools were analyzed by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Compared with conventional tools, the tool modifications reduced the flank wear by 45% for the investigated cutting parameters. Furthermore, we were able to significantly increase the cutting speed and feed rate without failure of the tool. The investigated surface modifications have great potential to enhance the productivityof metal cutting processes.

  • 79.
    Hoier, Philipp
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science,Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science,Gothenburg, Sweden.
    Tamil Alagan, Nageswaran
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Flank wear characteristics of WC-Co tools when turning Alloy 718 with high-pressure coolant supply2017In: Journal of Manufacturing Processes, E-ISSN 2212-4616, Vol. 30, no Supplement C, p. 116-123Article in journal (Refereed)
    Abstract [en]

    In the present study, the tool wear mechanisms of uncoated cemented tungsten carbide (WC-Co) tools during machining Alloy 718 with high-pressure coolant supply are investigated. Worn flank faces are analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). With increasing spiral cutting length, larger areas on the tool surface are subjected to erosion of Co-binder by the coolant jet impact. Moreover, the amount and morphology of workpiece-precipitates adhered on worn flank surfaces are influenced significantly by the extent of flank wear land (due to increasing spiral cutting length). The reasons for the obtained results are addressed with respect to the underlying mechanisms. Possible implications for the tool wear behavior are discussed.

  • 80.
    Holmberg, Jonas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Surface integrity on post processed alloy 718 after nonconventional machining2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is a strong industrial driving force to find alternative production technologies in order to make the production of aero engine components of superalloys even more efficient than it is today. Introducing new and nonconventional machining technologies allows taking a giant leap to increase the material removal rate and thereby drastically increase the productivity. However, the end result is to meet the requirements set for today's machined surfaces.The present work has been dedicated to improving the knowledge of how the non-conventional machining methods Abrasive Water Jet Machining, AWJM, Laser Beam Machining, LBM, and Electrical Discharge Machining, EDM, affect the surface integrity. The aim has been to understand how the surface integrity could be altered to an acceptable level. The results of this work have shown that both EDM and AWJM are two possible candidates but EDM is the better alternative; mainly due to the method's ability to machine complex geometries. It has further been shown that both methods require post processing in order to clean the surface and to improve the topography and for the case of EDM ageneration of compressive residual stresses are also needed.Three cold working post processes have been evaluated in order to attain this: shot peening, grit blasting and high pressure water jet cleaning, HPWJC. There sults showed that a combination of two post processes is required in order to reach the specified level of surface integrity in terms of cleaning and generating compressive residual stresses and low surface roughness. The method of high pressure water jet cleaning was the most effective method for removing the EDM wire residuals, and shot peening generated the highest compressive residual stresses as well as improved the surface topography.To summarise: the most promising production flow alternative using nonconventional machining would be EDM followed by post processing using HPWJC and shot peening.

  • 81.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea IVF AB, Argongatan 30, Mölndal SE-431 53, Sweden.
    Prieto, Juan Manuel Rodri­guez
    Luleå University of Technology, Division of Mechanics of Solid Materials Department of Engineering Sciences and Mathematics. Luleå SE-971 87, Sweden.
    Berglund, Johan
    Swerea IVF AB, Argongatan 30, Mölndal SE-431 53, Sweden.
    Sveboda, Ales
    Luleå University of Technology, Division of Mechanics of Solid Materials Department of Engineering Sciences and Mathematics. Luleå SE-971 87, Sweden.
    Jonsén, Pärr
    Luleå University of Technology, Division of Mechanics of Solid Materials Department of Engineering Sciences and Mathematics. Luleå SE-971 87, Sweden.
    Experimental and PFEM-simulations of residual stresses from turning tests of a cylindrical Ti-6Al-4V shaft2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 71, p. 144-149Article in journal (Refereed)
    Abstract [en]

    Alloy Ti-6Al-4V is a frequently used material in aero space applications due the high strength and low weight. This material is however often considered as a difficult to machine alloy due to several material properties such as the inherent characteristics of high hot hardness and strength which is causing an increased deformation of the cutting tool during machining. The thermal properties also cause a low thermal diffusion from locally high temperatures in the cutting zone that allows for reaction to the tool material resulting in increased tool wear. Predicting the behavior of machining of this alloy is therefore essential when selecting machining tools or machining strategies. If the surface integrity is predicted, the influence of different machining parameters could be studied using Particle Finite Element (PFEM)-simulations. In this investigation the influence from cutting speed and feed during turning on the residual stresses has been measured using x-ray diffraction and compared to PFEM-simulations. The results showed that cutting speed and feed have great impact on the residual stress state. The measured cutting force showed a strong correlation especially to the cutting feed. The microstructure, observed in SEM, showed highly deformed grains at the surface from the impact of the turning operation and the full width half maximum from the XDR measurements distinguish a clear impact from different cutting speed and feed which differed most for the higher feed rate. The experimental measurements of the residual stresses and the PFEM simulations did however not correlate. The surface stresses as well as the sign of the residuals stresses differed which might be due to the material model used and the assumption of using a Coulomb friction model that might not represent the cutting conditions in the investigated case.

  • 82.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea IVF AB, Argongatan 30, 431 22 Mölndal, Sweden.
    Steuwer, Axel
    Nelson Mandela Metropolitan University, Gardham Avenue, 6031 Port Elizabeth, South Africa.
    Stormvinter, Albin
    Swerea IVF AB, Argongatan 30, 431 22 Mölndal, Sweden.
    Kristofferson, Hans
    Swerea IVF AB, Argongatan 30, 431 22 Mölndal, Sweden.
    Haakanen, Merja
    Stresstech OY, Tikkutehtaantie 1, 40 800 Vaajakoski, Finland.
    Berglund, Johan
    Swerea IVF AB, Argongatan 30, 431 22 Mölndal, Sweden.
    Residual stress state in an induction hardened steel bar determined by synchrotron- and neutron diffraction compared to results from lab-XRD2016In: Materials Science and Engineering: A, ISSN 0921-5093, Vol. 667, p. 199-207Article in journal (Refereed)
    Abstract [en]

    Induction hardening is a relatively rapid heat treatment method to increase mechanical properties of steel components. However, results from FE-simulation of the induction hardening process show that a tensile stress peak will build up in the transition zone in order to balance the high compressive stresses close to the surface. This tensile stress peak is located in the transition zone between the hardened zone and the core material. The main objective with this investigation has been to non-destructively validate the residual stress state throughout an induction hardened component. Thereby, allowing to experimentally confirming the existence and magnitude of the tensile stress peak arising from rapid heat treatment. For this purpose a cylindrical steel bar of grade C45 was induction hardened and characterised regarding the microstructure, hardness, hardening depth and residual stresses. This investigation shows that a combined measurement with synchrotron/neutron diffraction is well suited to non-destructively measure the strains through the steel bar of a diameter of 20 mm and thereby making it possible to calculate the residual stress profile. The result verified the high compressive stresses at the surface which rapidly changes to tensile stresses in the transition zone resulting in a large tensile stress peak. Measured stresses by conventional lab-XRD showed however that at depths below 1.5 mm the stresses were lower compared to the synchrotron and neutron data. This is believed to be an effect of stress relaxation from the layer removal. The FE-simulation predicts the depth of the tensile stress peak well but exaggerates the magnitude compared to the measured results by synchrotron/neutron measurements. This is an important knowledge when designing the component and the heat treatment process since this tensile stress peak will have great impact on the mechanical properties of the final component.

  • 83.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea-IVF AB, 431 22, Mölndal, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Berglund, Johan
    Grit Blasting for Removal of Recast Layer from EDM Process on Inconel 718 Shaft: An Evaluation of Surface Integrity2016In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 25, no 12, p. 5540-5550Article in journal (Refereed)
    Abstract [en]

    The heat generated during EDM melts the work material and thereby allows large amounts to be removed,but an unfavorable surface of a recast layer (RCL) will also be created. This layer has entirely different properties compared to the bulk. Hence, it is of great interest to efficiently remove this layer and to verify that it has been removed. The main objective of this work has been to study the efficiency of grit blasting forremoval of RCL on an EDM aero space shaft. Additionally, x-ray fluorescence (XRF) has been evaluated asa nondestructive measurement to determine RCL presence. The results show that the grit-blasting processing parameters have strong influence on the ability to remove RCL and at the same time introduce beneficial compressive stresses even after short exposure time. Longer exposure will remove the RCL fromthe surface but also increase the risk that a larger amount of the blasting medium will get stuck into the surface. This investigation shows that a short exposure time in combination with a short grit-blasting nozzle distance is the most preferable process setting. It was further found that handheld XRF equipment can be used as a nondestructive measurement in order to evaluate the amount of RCL present on an EDM surface.This was realized by analyzing the residual elements from the EDM wire.

  • 84.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Swerea-IVF AB, 431 22, Mölndal, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Berglund, Johan
    Swerea IVF AB, Argongatan 30, 431 22 Mölndal, Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Evaluation of surface integrity after high energy machining with EDM, Laser Beam Machining and Abrasive Water Jet Machining of Alloy 7182018In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015Article in journal (Other academic)
    Abstract [en]

    Development of future aero engine components based on new design strategies utilising topological optimisation and additive manufacturing has in the past years become a reality. This allows for designs that involve geometries of "free form" surfaces and material combinations that could be difficult to machine using conventional milling. Hence, alternative manufacturing routes using non-conventional high energy methods are interesting to explore. In this investigation, the three high energy machining methods abrasive water jet machining (AWJM), electrical discharge machining (EDM) and laser beam machining (LBM) have been compared in terms of surface integrity to the reference, a ball nosed end milled surface. The results showed great influence on the surface integrity from the different machining methods. It was concluded that AWJM resulted in the highest quality regarding surface integrity properties with compressive residual stresses in the surface region and a low surface roughness with texture from the abrasive erosion. Further, it was shown that EDM resulted in shallow tensile residual stresses in the surface and an isotropic surface texture with higher surface roughness. However, even though both methods could be considered as possible alternatives to conventional milling they require post processing. The reason is that the surfaces need to be cleaned from either abrasive medium from AWJM or recast layer from EDM. It was further concluded that LBM should not be considered as an alternative in this case due to the deep detrimental impact from the machining process.Keywords

  • 85.
    Holmberg, Jonas
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Manufacturing Swerea IVF AB Mölndal Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB Trollhättan Sweden.
    Berglund, Johan
    Manufacturing Swerea IVF AB Mölndal Sweden.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Surface integrity after post processing of EDM processed Inconel 718 shaft2018In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 95, no 5-8, p. 2325-2337Article in journal (Refereed)
    Abstract [en]

    Electrical discharge machining (EDM) is considered as an efficient alternative to conventional material removal concepts that allows for much higher material removal rates. However, EDM generates unwanted features such as re-cast layer (RCL), tensile residual stresses and a rough surface. In order to recover the surface integrity, different post processes has been compared: high-pressure water jet (HPWJ), grit blasting (GB) and shot peening (SP). Surface integrity has been evaluated regarding microstructure, residual stresses, chemical content and surface roughness. The results showed that a combination of two post processes is required in order to restore an EDM processed surface of discontinuous islands of RCL. HPWJ was superior for removing RCL closely followed by grit blasting. However, grit blasting showed embedded grit blasting abrasive into the surface. Regarding surface roughness, it was shown that both grit blasting and HPWJ caused a roughening of the surface topography while shot peening generates a comparably smoother surface. All three post processes showed compressive residual stresses in the surface where shot peening generated the highest amplitude and penetration depths. However, the microstructure close to the surface revealed that shot peening had generated cracks parallel to the surface. The results strongly state how important it is to evaluate the surface at each of the different subsequent process steps in order to avoid initiation of cracks.

  • 86.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Welding Technology.
    Engelberg, Dirk
    The University of Manchester, School of Materials, Manchester M13 9PL, UK.
    Roy, Matthew J.
    The University of Manchester, School of Mechanical, Aerospace and Civil Engineering,Manchester M13 9PL, UK.
    Kumara, Chamara
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    A novel arc heat treatment technique for producing graded microstructures through controlled temperature gradients2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 121, no May, p. 11-23Article in journal (Refereed)
    Abstract [en]

    This paper introduces a novel arc heat treatment technique to produce samples with graded microstructures through the application of controlled temperature gradients. Steady state temperature distributions within the sample can be achieved and maintained, for times ranging from a few seconds to several hours. The technique reduces the number of samples needed to characterize the response of a material to thermal treatments, and can consequently be used as a physical simulator for materials processing. The technique is suitable for conventional heat treatment analogues, welding simulations, multi-step heat treatments, and heat treatments with controlled heating and cooling rates. To demonstrate this technique, a super duplex stainless steel was treated with a stationary TIG arc, to confirm the relationship between generated steady-state temperature fields, microstructure development, hardness, and sensitization to corrosion. Metallographic imaging and hardness mapping provided information about graded microstructures, confirming the formation of secondary phases and microstructure sensitization in the temperature range 850–950 °C. Modelling of temperature distributions and thermodynamic calculations of phase stabilities were used to simulate microstructure development and associated welding cycles.

  • 87.
    Hovling, David
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Martinsson, Petter
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Utvärdering av lagen om riktlinjer för kommunala markanvisningar (2014:899)2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Today, there is a major residential shortage in Sweden creating an immediate need to build more housing. The municipalities of Sweden with their monopoly on land ownership must make new housing a priority to ensure that the demand is met. Since January 1, 2015, municipalities have utilized land allocation as the primary means to build; however, they are in the process of adopting new guidelines. The purpose of this study focuses on whether or not guidelines are helpful to developers. Furthermore, it required the municipalities to track their guidelines and report any improvements with their land allocation. The purpose of this research was to qualitatively analyze the land allocations between the municipalities of Gothenburg and Stockholm to see of both follow their guidelines. It would also reveal their process for selecting a developer.

    The data was gathered from a survey sent to 100 different developers that had completed at least one application since 2015. The data collected revealed a substantial divide among the developers regarding their perspective on the law that regulate the land allocation process.

    The results of the survey revealed that the developers had varying views on the guideline processes. Some developers believed that the guidelines are helpful while others criticize that they do not properly fulfill its function. The developer's interviews and surveys revealed the legal significance of transparent reporting as to why the municipalities choose a specific developer. The survey also showed that developers preferred direct land allocations.

  • 88.
    Hulling, Ulf
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Virtual machining solutions: An experimental and case study approach in milling operations2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Recent developments into virtual machining from a research point of view in combination with experiences in a collaboration project with machining companies spawned the question of how complex it is to setup a virtual machining solution and if such a solution is accurate. In the herein presented thesis, a virtual machining solution consisting of cutting data selection, vibration management, machine tool dynamics modelling, tool path programming and geometrical verification, physics based cutting mechanics simulation, geometrically based optimization, physics based optimization, and postprocessing have been successfully setup, tested and described. The physics based cutting mechanics simulation have been compared to analytical force calculations and force measurements. Physics based cutting mechanics simulation were shown to be more accurate by a factor of almost two compared to analytical force calcula-tions. A smaller case study to compare different approaches to tool path optimization was per-formed and physics based optimization showed greater promise compared to geometrically based.

  • 89.
    Islavath, Nanaji
    et al.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India; School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046, India.
    Das, Dibakar
    School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ramasamy, Easwaramoorthi
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Seed layer-assisted low temperature solution growth of 3D ZnO nanowall architecture for hybrid solar cells2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 116, p. 219-226Article in journal (Refereed)
    Abstract [en]

    Aligned metal oxide nanostructures carry electrons efficiently, and are therefore ideal building blocks for next-generation optoelectronic devices. Herein, we report the seed-layer-assisted low-temperature solution growth of aligned 3D ZnO nanowall architecture on arbitrary substrates. By introducing a controlled amount of Al into a seed-layer, the morphology of ZnO nanostructure is gradually changed from nanowire to 3D nanowalls. Time-dependent growth experiments suggest that hydroxyl-ions present in growth solution react with Al to form Al(OH)4 which in turn binds to the positively charged Zn2 +surface and partially blocking ZnO growth along the (0001) direction and promoting lateral growth. Such aligned 3D ZnO nanowall architecture, with the unique combination of high surface-area and cage-like pores, grown on seed-layer coated transparent conductive substrate is found to be beneficial for electron transporting material (ETM) in perovskite solar cells and a maximum photocurrent density (JSC) of 7.5 mA.cm− 2 and a power conversion efficiency (η) of 2.4% are demonstrated. Our facile approach readily allows further growth of ZnO nanowires on 3D ZnO nanowall surface; thereby improving the perovskite-ZnO interface and increasing the JSC and η to 9.7 and 3.3%, respectively. This 3D ZnO nanowall-nanowire architecture opens up a novel configuration for designing high-performance optoelectronic devices.

  • 90.
    Islavath, Nanaji
    et al.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Saroja, S.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Reddy, K Srinivas
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Harikesh, P.C.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Veerappan, G.
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Ramasamy, Easwaramoorthi
    Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India.
    Effect of hole-transporting materials on the photovoltaic performance and stability of all-ambient-processed perovskite solar cells2017In: Journal of Energy Chemistry, ISSN 2095-4956, Vol. 26, no 3, p. 584-591Article in journal (Refereed)
    Abstract [en]

    High-efficiency perovskite solar cells (PSCs) reported hitherto have been mostly prepared in a moisture and oxygen-free glove-box atmosphere, which hampers upscaling and real-time performance assessment of this exciting photovoltaic technology. In this work, we have systematically studied the feasibility of all-ambient-processing of PSCs and evaluated their photovoltaic performance. It has been shown that phase-pure crystalline tetragonal MAPbI3 perovskite films are instantly formed in ambient air at room temperature by a two-step spin coating process, undermining the need for dry atmosphere and post-annealing. All-ambient-processed PSCs with a configuration of FTO/TiO2/MAPbI3/Spiro-OMeTAD/Au achieve open-circuit voltage (990 mV) and short-circuit current density (20.31 mA/cm2) comparable to those of best reported glove-box processed devices. Nevertheless, device power conversion efficiency is still constrained at 5% by the unusually low fill-factor of 0.25. Dark current–voltage characteristics reveal poor conductivity of hole-transporting layer caused by lack of oxidized spiro-OMeTAD species, resulting in high series-resistance and decreased fill-factor. The study also establishes that the above limitations can be readily overcome by employing an inorganic p-type semiconductor, copper thiocyanate, as ambient-processable hole-transporting layer to yield a fill-factor of 0.54 and a power conversion efficiency of 7.19%. The present findings can have important implications in industrially viable fabrication of large-area PSCs.

    The poor conductivity of ambient-processed spiro-OMeTAD HTM layer caused by lack of oxidation is identified as a major performance limiting factor and successfully overcome by replacing with stable inorganic CuSCN.

  • 91.
    Jafari, R.
    et al.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, 14115, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, T.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, 14115, Iran.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    KCI-induced corrosion behavior of HVAF-sprayed Ni-based coatings in ambient air2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), Curran Associates, Inc. , 2017, Vol. 2, p. 946-950Conference paper (Refereed)
    Abstract [en]

    It is well known that the presence of KCl deposited on superheater tubes in biomass- and waste-fired boilers leads to a severe corrosion and premature damage. In order to protect such critical components which are routinely exposed to aggressive environments, thermal spray coatings are frequently proposed as a potential solution. By virtue of the techno-commercial benefits that provides as a direct outcome of its ability to cost-effectively deposit coatings virtually free of porosity and in situ formed oxides, the high velocity air-fuel (HVAF) process offers a particularly attractive approach. In the present work, the influence of KCl on the oxidation behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5AI, Ni21Cr7AI1Y, and Ni21Cr9Mo) has been investigated. The coatings were deposited onto specimens of 16Mo3 steel, a widely used boiler tube material. High temperature corrosion tests were carried out in ambient air at 600°C, with 0.1 mg/cm2 KCl being sprayed onto the samples prior to the exposure. Uncoated substrates and an identical test environment without KCl were used as reference. SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples. The results showed that the small addition of KCl significantly accelerated damage to the coatings. It was further revealed that the alumina-forming NiAl coating was capable of forming a more protective oxide scale compared to other chromia and mixed-oxide scale forming coatings. In general, the oxidation resistance of the coatings based on the kinetic studies had the following ranking (from the best to the worst): NiAl >NiCr> NiCrAlY> NiCrMo. © Copyright 2017 by DVS Media GmbH. All rights reserved.

  • 92.
    Jafari, R.
    et al.
    Department of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, T.
    Department of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran .
    Markocsan, Nicolaie
    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.
    KCl-induced corrosion behavior of HVAF-sprayed Ni-based coatings in ambient air2017Conference paper (Other academic)
  • 93.
    Jafari, Reza
    et al.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, Taghi
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Huhtakangas, Matti
    M. H. Engineering AB, Karlskoga, Sweden .
    Markocsan, Nicolaie
    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.
    KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 500-511Article in journal (Refereed)
    Abstract [en]

    KCl-induced high temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y, and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168h. The coatings were deposited onto 16Mo3 steel - a widely used boiler tube material.Uncoated substrate, 304L and Sanicro25 were used as reference materials in the test environment.SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples.The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for Page 1 of 23ASM the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al >Ni21Cr> Ni21Cr7Al1Y>Ni21Cr9Mo.

  • 94.
    Johansson, Tobias
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Modernisering av el- och belysningssystem i en industrifastighet2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been carried out in AB Järn & Rörs premises in Lilla Edet, The project was to modernize the electricity and lighting in the premises, and also calculate how much a modernized lighting solution can save in energy. The premises included a metal workshop, garage, hallway, bath and dressing room, staff room, office and a storage room. The project has been carried out in accordance with current regulations, standards and recommendations from the Swedish National Electrical Safety Board and the Swedish work environment authority. The number of power outlets have been increased in all of the rooms to comply with current standards. The Lightning has been changed from 69 luminaries equipped with two 33 W T5 Light Tubes each and a few halogen lamps, to 59 luminaries equipped with LED light tubes of varying power. This change has decreased the amount of power required by the lighting system from 4167 W to 2246 W, which is a decrease of 1921 W or 46%. The electrical blueprints have all been created in the program EasyEl. The placement of the luminaries and the light calculations have all been made in the program DIALux.

  • 95.
    Jonnalagadda, K.P.
    et al.
    Linköping University.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Li, X-H.
    Siemens Industrial Turbomachinary, Finspång, Sweden.
    Markocsan, Nicolaie
    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.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Peng, R.L.
    Trebacher Indiustrie, Austria.
    Hot corrosion behavior of multi-layer suspension plasma sprayed Gd2Zr2O7 /YSZ thermal barrier coatings2016In: Thermal Spray 2016: Proceedings from the International Thermal Spray Conference in Shanghai, P.R China, May 10-12, 2016, DVS Media GmbH , 2016, Vol. 324, p. 261-266Conference paper (Refereed)
  • 96.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB,Finspång,Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

  • 97.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nicholas, Curry
    Treibacher Ind AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    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.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO42017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1-2, p. 140-149Article in journal (Refereed)
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  • 98.
    Jonnalagadda, Krishna Praveen
    et al.
    Linkoping University, Department of Manangement and Engineering,Linkoping, Sweden.
    Peng, Ru Lin
    Linkoping University, Department of Manangement and Engineering,Linkoping, Sweden.
    Mahade, Satyapal
    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.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspang, Sweden.
    Hot corrosion behavior of multi-layer suspension plasma sprayed Gd2Zr2O7/YSZ thermal barrier coatings2017In: InterCeram: International Ceramic Review, ISSN 0020-5214, Vol. 66, no 5, p. 180-184Article in journal (Refereed)
    Abstract [en]

    This study investigates the corrosion resistance of double layer Gd2Zr2O7/YSZ, triple layer dense Gd2Zr2O7 / Gd2Zr2O7/YSZ and a reference single layer YSZ coating with a similar overall top coat thickness of 300-320 Όm. All the coatings were manufactured by suspension plasma spraying (SPS), resulting in a columnar structure. Corrosion tests were conducted at 900°C for 8 hours using vanadium pentoxide and sodium sulphate as corrosive salts at a concentration of 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7 coatings exhibited lower corrosion resistance than the reference material, YSZ. Reaction between the corrosive salts and Gd2Zr2O7 results in the formation of gadolinium vanadate ( GdVO4) along the top surface and between the columns. While the stresses due to phase transformation of zirconia can be relieved to some extent by realigning of the columns in the top coat, it is believed that GdVO4 formation between the columns, along with low fracture toughness of Gd2Zr2O7 had resulted in lower corrosion resistance. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top, as a preventive layer for salt infiltration, did not improve the corrosion resistance.

  • 99.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Coating formation by solution precursor plasma spraying and prospects for powder-solution hybrid processing2016Conference paper (Other academic)
  • 100.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Experiences of spraying fine powders dissolved in alcohol or water2016Conference paper (Other academic)
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