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  • 1.
    Chen, Y.
    et al.
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Zhao, X.
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, Shanghai, China .
    Dang, Y.
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Xiao, Ping
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Characterization and understanding of residual stresses in a NiCoCrAlY bond coat for thermal barrier coating application2015Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 94, s. 1-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The residual stresses in a NiCoCrAlY bond coat deposited on a Ni-base superalloy substrate after oxidation at 1150 °C were studied by X-ray diffraction using the sin2Ψ technique. The stresses were found to be tensile; they first increased and then decreased with oxidation time. High temperature stress measurement indicated that the stress developed and built up upon cooling, predominantly within the temperature range from 1150 °C to 600 °C. Microstructural examination suggested that, due to the limited penetration depth into the bond coat, the X-ray only probed the stress in a thin surface layer consisting of the single γ-phase formed through Al depletion during oxidation. Quantitative high temperature X-ray diffraction analysis revealed that, above 600 °C, the volume fraction of the β-phase in the bond coat increased with decreasing temperature. The mechanisms of stress generation in the bond coat were examined and are discussed based on the experiments designed to isolate the contribution of possible stress generation factors. It was found that the measured bond coat stresses were mainly induced by the volume change of the bond coat associated with the precipitation of the β-phase upon cooling.

  • 2.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Design of Thermal Barrier Coating Systems2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Thermal barrier coatings (TBC’s) are used to provide both thermal insulation and oxidation protection to high temperature components within gas turbines. The development of turbines for power generation and aviation has led to designs where the operation conditions exceed the upper limits of most conventional engineering materials. As a result there has been a drive to improve thermal barrier coatings to allow the turbine to operate at higher temperatures for longer.

    The focus of this thesis has been to design thermal barrier coatings with lower conductivity and longer lifetime than those coatings used in industry today. The work has been divided between the development of new generation air plasma spray (APS) TBC coatings for industrial gas turbines and the development of suspension plasma spray (SPS) TBC systems.

    The route taken to achieve these goals with APS TBC’s has been twofold. Firstly an alternative stabiliser has been chosen for the zirconium oxide system in the form of dysprosia. Secondly, control of the powder morphology and spray parameters has been used to generate coating microstructures with favourable levels of porosity.

    In terms of development of SPS TBC systems, these coatings are relatively new with many of the critical coating parameters not yet known. The focus of the work has therefore been to characterise their lifetime and thermal properties when produced in a complete TBC system.

    Results demonstrate that dysprosia as an alternative stabiliser gives a reduction in thermal conductivity. While small at room temperature and in the as produced state; the influence becomes more pronounced at high temperatures and with longer thermal exposure time. The trade-off for this lowered thermal conductivity may be in the loss of high temperature stability. Overall, the greatest sustained influence on thermal conductivity has been from creating coatings with high levelsof porosity.

    In relation to lifetime, double the thermo-cyclic fatigue (TCF) life relative to the industrial standard was achieved using a coating with engineered porosity. Introducing a polymer to the spray powder helps to generate large globular pores within the coating together with a large number of delaminations. Such a structure was shown to be highly resistant to TCF testing.

    SPS TBC’s were shown to have much greater performance relative to their APS counterparts in thermal shock life, TCF life and thermal conductivity. Columnar SPS coatings are a prospective alternative for strain tolerant coatings in gas turbine engines.

  • 3.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Design of Thermal Barrier Coating Systems2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Thermal barrier coatings (TBC’s) are used to provide both thermal insulation and oxidation protection to high temperature components within gas turbines. The development of turbines for power generation and aviation has led to designs where the operation conditions exceed the upper limits of most conventional engineering materials. As a result there has been a drive to improve thermal barrier coatings to allow the turbine to operate hotter for longer.

    The focus of this study has been the development of a new generation of TBC system for industrial implementation. The goal for these new coatings was to achieve lower conductivity and longer lifetime than those coatings used today. The route taken to achieve these goals has been twofold. Firstly an alternative stabiliser has been chosen for the zirconium oxide system in the form of dysprosia. Secondly, Control of the powder morphology and spray parameters has been used to generate coating microstructures with favourable levels of porosity.

    Samples have been heavily characterised using the laser flash technique for evaluation of thermal properties. Measurements were performed at room temperature and at intervals up to 1200°C. Samples have also been tested in their as produced state and after heat treatments of up to 200 hours.

    Lifetime evaluation has been performed using the thermo-cyclic fatigue test to expose coating systems to successive cycles of heating and cooling combined with oxidation of the underlying metallic coating.

    Microstructures have been prepared and analysed using SEM. An image analysis routine has been used to attempt to quantify changes in microstructure features between coating types or coating exposure times and to relate those changes to changes in thermal properties

    Results show that dysprosia as an alternative dopant gives a reduction in thermal conductivity. While small at room temperature and in the as produced state; the influence becomes more pronounced at high temperatures and with thermal exposure time. Overall, the greatest sustained influence on thermal conductivity has been from creating coatings with high levels of porosity.

    In relation to lifetime, the target of double the thermo-cyclic fatigue life was achieved using a coating with engineered porosity. Introducing a polymer to the spray powder helps to generate large globular pores within the coating together with a large number of delaminations. Such a structure has shown to be highly resistant to TCF testing.

  • 4.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik. Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Treibacher AG, Austria.
    Feedstock for SPS and SPPS: Properties and Processing2016Konferensbidrag (Övrigt vetenskapligt)
  • 5.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Suspension plasma spray: how suspension properties and spray parameters influence coating possibilities2016Konferensbidrag (Övrigt vetenskapligt)
  • 6.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Donoghue, Jack
    University of Manchester.
    Evolution of thermal conductivity of dysprosia stabilised thermal barrier coating systems during heat treatment2012Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, ISSN 0257-8972, Vol. 209, s. 38-43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dysprosia stabilised zirconia coatings offer a potential reduction in thermal heat transfer for thermal barrier coating systems with the added benefit of being producible with existing equipment and spray knowledge. However, there is little information on the long term performance of such systems relative to the standard coatings. While a low thermal conductivity is important for a gas turbine; sintering resistance is important to maintain properties over the lifetime of a component.

    In this study, four dysprosia stabilised zirconia coatings are compared with a standard yttria stabilised coating in present industrial use.

    Samples were exposed to isothermal furnace conditions at 1150 °C from 5 to 200 hours to observe the sintering resistance of the coating systems. Tests carried out include microstructural analysis with SEM, thermal conductivity measurements using laser flash analysis and porosity changes monitored using image analysis.

  • 7.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Janikowski, Wysomir
    University of Manchester.
    Pala, Zdenek
    Academy of Sciences of the Czech Republic, Institute of Plasma Physics.
    Vilémová, Monica
    Academy of Sciences of the Czech Republic, Institute of Plasma Physics.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Impact of Impurity Content on the Sintering Resistance and Phase Stability of Dysprosia- and Yttria-Stabilized Zirconia Thermal Barrier Coatings2014Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, nr 1-2, s. 160-169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dysprosia-stabilized zirconia (DySZ) is a promising candidate to replace yttria-stabilized zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high-temperature sintering behavior. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and YSZ coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 h at a temperature of 1150 °C. Samples were measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes. Phase analysis utilizing x-ray diffraction was used to determine differences in phase degradation of the coatings after heat treatment. © 2013 ASM International.

  • 8.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Janikowski, Wyszomir
    University of Mancheste.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Impact of impurity content on the sintering resistance of dysprosia and yttria stabilised zirconia thermal barrier coatings2013Ingår i: 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, s. 557-563Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dysprosia stabilised zirconia (DySZ) is a promising candidate to replace yttria stabilised zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high temperature sintering behaviour. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and yttria stabilised zirconia coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 hours at a temperature of 1150°C. Samples were subsequently measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes due to sintering.

  • 9.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Goddard, Caroline
    Manchester University.
    Influence of Sensor contact on the Thermal Conductivity Values of Thermal Barrier Coatings: Part 1 Experimental2010Ingår i: Proceedings of the 24th International Conference on Surface Modification Technologies: 7-9 sept, Dresden, 2010, s. 317-327Konferensbidrag (Refereegranskat)
  • 10.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Li, Xin-Hai
    Siemens Turbomachinery.
    Tricoire, Aurelien
    Volvo Aero Corp.
    Dorfman, Mitch
    Sulzer Metco.
    Next Generation Thermal Barrier Coatings for the Gas Turbine Industry2010Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, ISSN 1059-9630, Vol. 20, nr 1-2, s. 108-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study is to develop the next generation of production ready air plasma sprayed thermalbarrier coating with a low conductivity and long lifetime. A number of coating architectures wereproduced using commercially available plasma spray guns. Modifications were made to powder chemistry,including high purity powders, dysprosia stabilized zirconia powders, and powders containingporosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologieswere used to attain beneficial microstructures. Dual layer coatings were produced using the two powders.Laser flash technique was used to evaluate the thermal conductivity of the coating systems from roomtemperature to 1200 C. Tests were performed on as-sprayed samples and samples were heat treated for100 h at 1150 C. Thermal conductivity results were correlated to the coating microstructure using imageanalysis of porosity and cracks. The results show the influence of beneficial porosity on reducing thethermal conductivity of the produced coatings.

  • 11.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Tricoire, Aurélien
    Volvo Aero, Trollhättan.
    Dorfman, Mitch
    Sulzer Metco, Westbury, United States.
    Next generation thermal barrier coatings for the gas turbine industry2011Ingår i: Journal of Thermal Spray Technology, Vol. 20, nr 1-2, s. 108-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings. © 2010 ASM International.

  • 12.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång.
    Dorfman, Mitch
    Sulzer Metco, Westbury, USA.
    Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems2013Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 22, nr 6, s. 864-872Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was the further development of dysprosia stabilised zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial stan dard thermal barrier coating. Two morphologies of ceramic top coat were studied; one using a dual layer systems and the second using a polymer to generate porosity. Evaluations were carried out using laser flash technique to measure thermal properties. Lifetime testing was conducted using thermal shock testing and thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis used to characterise porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

  • 13.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Tang, Zhaolin
    Northwest Mettech Corp., Vancouver, Canada.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Influence of Bond Coat Surface Roughness on the Structure of Axial Suspension Plasma Spray Thermal Barrier Coatings - Thermal and Lifetime Performance2015Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, nr April, s. 15-23Artikel i tidskrift (Refereegranskat)
  • 14.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA .
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings2014Ingår i: Coatings, ISSN 2079-6412, Vol. 4, nr 3, s. 630-650Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM

  • 15.
    Curry, Nicholas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser. Treibacher Industrie AG, Althofen 9330, Austria.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Susnjar, Johann
    Treibacher Industrie AG, Althofen 9330, Austria.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Performance Testing of Suspension Plasma Sprayed Thermal Barrier Coatings Produced with Varied Suspension Parameters2015Ingår i: Coatings, ISSN 2079-6412, Vol. 5, nr 3, s. 338-356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suspension plasma spraying has become an emerging technology for the production of thermal barrier coatings for the gas turbine industry. Presently, though commercial systems for coating production are available, coatings remain in the development stage. Suitable suspension parameters for coating production remain an outstanding question and the influence of suspension properties on the final coatings is not well known. For this study, a number of suspensions were produced with varied solid loadings, powder size distributions and solvents. Suspensions were sprayed onto superalloy substrates coated with high velocity air fuel (HVAF) -sprayed bond coats. Plasma spray parameters were selected to generate columnar structures based on previous experiments and were maintained at constant to discover the influence of the suspension behavior on coating microstructures. Testing of the produced thermal barrier coating (TBC) systems has included thermal cyclic fatigue testing and thermal conductivity analysis. Pore size distribution has been characterized by mercury infiltration porosimetry. Results show a strong influence of suspension viscosity and surface tension on the microstructure of the produced coatings.

  • 16.
    Ganvir, Ashish
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Characterization of Microstructure and Thermal Properties of YSZ Coatings Obtained by Axial Suspension Plasma Spraying (ASPS)2015Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, nr 7, s. 1195-1204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper aims at demonstrating various microstructures which can be obtained using the suspension spraying technique and their respective significance in enhancing the thermal insulation property of a thermal barrier coating. Three different types of coating microstructures are discussed which were produced by the Axial Suspension Plasma Spraying. Detailed characterization of coatings was then performed. Optical and scanning electron microscopy were utilized for microstructure evaluations; x-ray diffraction for phase analysis; water impregnation, image analysis, and mercury intrusion porosimetry for porosity analysis, and laser flash analysis for thermal diffusivity measurements were used. The results showed that Axial Suspension Plasma Spraying can generate vertically cracked, porous, and feathery columnar-type microstructures. Pore size distribution was found in micron, submicron, and nanometer range. Higher overall porosity, the lower density of vertical cracks or inter-column spacing, and higher inter-pass porosity favored thermal insulation property of the coating. Significant increase in thermal diffusivity and conductivity was found at higher temperature, which is believed to be due to the pore rearrangement (sintering and pore coarsening). Thermal conductivity values for these coatings were also compared with electron beam physical vapor deposition (EBPVD) thermal barrier coatings from the literature and found to be much lower. © 2015 ASM International

  • 17.
    Ganvir, Ashish
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Govindarajan, Sivakumar
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), 500005 Hyderabad, India.
    Characterization of Thermal Barrier Coatings Produced by Various Thermal Spray Techniques Using Solid Powder, Suspension, and Solution Precursor Feedstock Material2016Ingår i: International Journal of Applied CeramicTechnology, ISSN 1546-542X, Vol. 13, nr 2, s. 324-332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Use of a liquid feedstock in thermal spraying (an alternative to the conventional solid powder feedstock) is receiving an increasing level of interest due to its capability to produce the advanced submicrometer/nanostructured coatings. Suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS) are those advanced thermal spraying techniques which help to feed this liquid feedstock. These techniques have shown to produce better performance thermal barrier coatings (TBCs) than conventional thermal spraying. In this work, a comparative study was performed between SPS- and SPPS-sprayed TBCs which then were also compared with the conventional atmospheric plasma-sprayed (APS) TBCs. Experimental characterization included SEM, porosity analysis using weight difference by water infiltration, thermal conductivity measurements using laser flash analysis, and lifetime assessment using thermo-cyclic fatigue test. It was concluded that SPS coatings can produce a microstructure with columnar type features (intermediary between the columnar and vertically cracked microstructure), whereas SPPS can produce vertically cracked microstructure. It was also shown that SPS coatings with particle size in suspension (D50) <3 μm were highly porous with lower thermal conductivity than SPPS and APS coatings. Furthermore, SPS coatings have also shown a relatively better thermal cyclic fatigue lifetime than SPPS.

  • 18.
    Ganvir, Ashish
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Joshi, Shrikant
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Vilemova, Monika
    IPP.
    Pala, Zdenek
    IPP.
    Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings2016Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, nr 1-2, s. 202-212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  • 19.
    Ganvir, Ashish
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd Forskningsmiljön industriprocesser.
    Toma, Filofteia-Laura
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Comparative study of suspension plasma sprayed and suspension high velocity oxy-fuel sprayed YSZ thermal barrier coatings2015Ingår i: Surface and Coatings Technology, ISSN 0257-8972, Vol. 268, s. 70-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suspension Thermal Spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings. This technique enables the production of much different performance thermal barrier coatings than conventional thermal spraying which uses solid powder as a feedstock material. In this work a comparative study is performed on four different types of thermal barrier coatings sprayed with two different thermal spay processes, suspension high velocity oxy-fuel spraying (SHVOF) and suspension plasma spraying (SPS) using two different water-based suspensions. Tests carried out include microstructural analysis with SEM, porosity analysis using weight difference by water infiltration, thermal conductivity measurements using laser flash analysis and lifetime assessment using thermo-cyclic fatigue tests. The results showed that SPS coatings were much porous and hence showed lower thermal conductivity than SHVOF coatings produced with the same suspension. From the thermo-cycling tests it was observed that the SPS coatings showed a higher lifetime than the SHVOF ones.

  • 20.
    Ganvir, Ashish
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Vilemova, Monika
    IPP Prague, Czech Republic.
    Pala, Zdenek
    IPP Prague, Czech Republic.
    Influence of Microstructure on Thermal Properties of Columnar Axial Suspension Plasma Sprayed Thermal Barrier Coatings2015Ingår i: Proceedings of the International Thermal Spray Conference: International Thermal Spray Conference and Exposition, ITSC 2015; Long Beach; United States; 11 May 2015 through 14 May 2015 / [ed] A. McDonald, A. Agarwal, G. Bolelli, A. Concustell, Y.-C. Lau, F.-L. Toma, E. Turunen, C. Widener, ASM International, 2015, s. 498-505Konferensbidrag (Refereegranskat)
    Abstract [en]

    Suspension Plasma Spraying is a relatively new thermal spraying technique to produce advanced thermal barrier coatings. This technique enables the production of a variety of structures from highly dense, highly porous, segmented or columnar coatings. In this work a comparative study is performed on six different suspension plasma sprayed thermal barrier coatings which were produced using axial injection and different process parameters. The influence of coating morphology and porosity on thermal properties was of specific interest. Tests carried out include microstructural analysis with SEM, phase analysis using XRD, porosity calculation using Archimedes experimental setup, pore distribution analysis using mercury infiltration technique and thermal diffusivity/conductivity measurements using laser flash analysis. The results showed that columnar and cauliflower type coatings were produced by axial suspension plasma spraying process. Better performance coatings were produced with relatively higher overall energy input given during spraying. Coatings with higher energy input, lower thickness and wider range of submicron and nanometer sized pores distribution showed lower thermal diffusivity and hence lower thermal conductivity. Also, in-situ heat treatment did not show dramatic increase in thermal properties.

  • 21.
    Gupta, Mohit Kumar
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Vaßen, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Design of Next Generation Thermal Barrier Coatings- Experiments and Modelling2013Ingår i: Surface and Coatings Technology, ISSN 0257-8972, Vol. 220, s. 20-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal barrier coating (TBC) systems have been used in the gas turbine industry since the 1980's. The future needs of both the air and land based turbine industry involve higher operating temperatures with longer lifetime on the component so as to increase power and efficiency of gas turbines. The aim of this study was to meet these future needs by further development of zirconia coatings. The intention was to design a coating system which could be implemented in industry within the next three years. Different morphologies of ceramic topcoat were evaluated; using dual layer systems and polymers to generate porosity. Dysprosia stabilised zirconia was also included in this study as a topcoat material along with the state-of-the-art yttria stabilised zirconia (YSZ). High purity powders were selected in this work. Microstructure was assessed with scanning electron microscope and an in-house developed image analysis routine was used to characterise porosity content. Evaluations were carried out using the laser flash technique to measure thermal conductivity. Lifetime was assessed using thermo-cyclic fatigue testing. Finite element analysis was utilised to evaluate thermal-mechanical material behaviour and to design the morphology of the coating with the help of an artificial coating morphology generator through establishment of relationships between microstructure, thermal conductivity and stiffness. It was shown that the combined empirical and numerical approach is an effective tool for developing high performance coatings. The results show that large globular pores and connected cracks inherited within the coating microstructure result in a coating with best performance. A low thermal conductivity coating with twice the lifetime compared to the industrial standard today was fabricated in this work.

  • 22.
    Jonnalagadda, K.P.
    et al.
    Linköping University.
    Mahade, Satyapal
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Li, X-H.
    Siemens Industrial Turbomachinary, Finspång, Sweden.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylen, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Peng, R.L.
    Trebacher Indiustrie, Austria.
    Hot corrosion behavior of multi-layer suspension plasma sprayed Gd2Zr2O7 /YSZ thermal barrier coatings2016Ingår i: 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, s. 261-266Konferensbidrag (Refereegranskat)
  • 23.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Linköping, 581 83, Sweden.
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering, Linköping, 581 83, Sweden.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Linköping, 581 83, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, 581 83, Sweden.
    Mahade, Satyapal
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finsping, SE-61283, Sweden.
    Failure of multi-layer suspension plasma sprayed thermal barrier coatings in the presence of Na2SO4 and NaCI at 900 °C2018Ingår i: Proceedings of the International Thermal Spray Conference, Vol. 2018-May, s. 8-15Artikel i tidskrift (Refereegranskat)
    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 (SPS) 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 °C and 900 °C with an exposure time of 8h at 900 °C. 75 wt. % Na2SO4 + 25 wt.% NaCI 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 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 coating edges and caused damage to develop relatively more from the edge. © 2018 ASM International® All rights reserved.

  • 24.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Treibacher Ind AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylen, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    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 + Na2SO42017Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, nr 1-2, s. 140-149Artikel i tidskrift (Refereegranskat)
    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.

  • 25.
    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
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    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 coatings2017Ingår i: InterCeram: International Ceramic Review, ISSN 0020-5214, Vol. 66, nr 5, s. 180-184Artikel i tidskrift (Refereegranskat)
    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.

  • 26.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Medricky, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Mušálek, Radek
    Institute of Plasma Physics CAS..
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Fatigue crack growth in bodies with thermally sprayed coating2015Ingår i: Proceedings from the International Thermal Spray Conference (May 11–14, 2015, Long Beach, California, USA), ASM International, 2015, Vol. 1, s. 398-405Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the spatiotemporal localization of crack initiation and the dynamics of crack propagation are studied. The resonance bending fatigue test is employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical TBC YSZ/NiCoCrAlY composites were tested. The strain distribution on the coating surface is evaluated by the digital image correlation method (DIC) through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e. the changes of material properties, crack initiation, and crack propagation are identified. The tested coatings strongly influenced the first two phases, the influence on the crack propagation was less significant. © Copyright (2015) by ASM International All rights reserved.

  • 27.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Čapek, Jiří
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Pala, Zdeněk
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Resonance bending fatigue testing with simultaneous damping measurement and its application on layered coatings2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, Part 2, s. 300-309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain εyy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann (2004) and classical dislocation model of Granato and LÌcke (1956). It appears, that the damping spectra can be well approximated as a combination of two defect peaks (C1 and C2) and one dislocation peak (D1). The low strain defect peak (peak C1) is sensitive to the presence of fatigue cracks. The second defect peak (peak C2) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C1 peak changes need to be found yet, however. In the crack growth stage II., both resonance frequency and peak height C1 correlate with the measured fatigue crack size.

  • 28.
    Kovářík, Ondřej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Čapek, Jiří
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Pala, Zdeněk
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Damping measurement during resonance fatigue test and its application for crack detection in TBC samples2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, nr Part 2, s. 300-309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain εyy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann [1] and classical dislocation model of Granato and LÌcke [2]. It appears, that the damping spectra can be well approximated as a combination of two defect peaks (C1 and C2) and one dislocation peak (D1). The low strain defect peak (peak C1) is sensitive to the presence of fatigue cracks. The second defect peak (peak C2) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C1 peak changes need to be found yet, however. In the crack growth stage II., both resonance frequency and peak height C1 correlate with the measured fatigue crack size.

  • 29.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Vassen, Robert
    Forschungszentrum Jülich.
    Erosion Behavior of Gadolinium Zirconate/YSZ Multi-Layered Thermal Barrier Coatings Deposited by Suspension Plasma Spray2016Ingår i: Proceedings of the International Thermal Spray Conference, 2016, s. 343-347Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 30.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Failure analysis of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings subjected to thermal cyclic fatigue2016Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 689, s. 1011-1019Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 31.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd Forskningsmiljön industriprocesser.
    Thermal conductivity and thermal cyclic fatigue of multilayered Gd2Zr2O7/YSZ thermal barrier coatings processed by suspension plasma spray2015Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 283, s. 329-336Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 32.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Vassen, Robert
    Forschungszentrum Julich, Inst Energy & Climate Res IEK 1, Julich, German.
    Functional performance of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings deposited by suspension plasma spray2017Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, s. 208-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 33.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Treibacher Industrie AGAlthofenAustria.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Vaßen, Robert
    Institute of Energy and Climate Research (IEK-1) Forschungszentrum Jülich GmbHJülich Germany.
    Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray2017Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, nr 1-2, s. 108-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 34.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Li, Ran
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Isothermal Oxidation Behavior of Gd2Zr2O7/YSZ Multilayered Thermal Barrier Coatings2016Ingår i: International Journal of Applied Ceramic Technology, ISSN 1546-542X, Vol. 13, nr 3, s. 443-450Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 35.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Effect of YSZ thickness on the thermal cyclic fatigue performance of gadolinium zirconate/YSZ double layered TBCs2018Ingår i: Proceedings of the International Thermal Spray Conference, s. 79-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) play a vital role in allowing the gas turbine engines to operate at high temperatures. With higher operating temperatures (>1200°C), the standard TBC material, 7-8wt. % Yttria Stabilized Zirconia (YSZ), is susceptible to CMAS (Calcium Magnesium Alumino Silicates) degradation and undesirable phase transformation. New TBC materials such as gadolinium zirconate (GZ) have shown to be capable of overcoming the challenges faced by YSZ. However, GZ has inferior fracture toughness relative to YSZ. In this work, three double layered TBC variations with different GZ and YSZ thickness respectively (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400GZ respectively, where the prefix numbers represent thickness in urn) were produced by suspension plasma spray (SPS) process. In all the three double layered TBC variations, the overall TBC thickness with GZ as the top layer and YSZ as the base layer was kept the same (500 urn). The objective was to investigate the influence of YSZ thickness on the thermal cyclic fatigue performance of GZ/YSZ double layered TBC. The as sprayed TBCs were characterized by SEM, XRD and porosity measurements and later subjected to thermal cyclic fatigue test at 1100°C. It was observed that the GZ/YSZ double layered TBC with lowest YSZ thickness (400GZ/100YSZ) showed higher thermal cyclic lifetime whereas the TBC with thicker YSZ layer (100GZ/400YSZ) showed lowest thermal cyclic fatigue lifetime. The failure analysis of the thermally cycled TBCs revealed similar failure modes, i.e. spallation of the top coat due to horizontal crack propagation within the thermally grown oxide (TGO). Furthermore, the ceramic top coats in all the three TBC variations after failure showed the widening of column gaps. © 2018 ASM International® All rights reserved.

  • 36.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Ruelle, Céline
    ENSIL, Limoges, Franc.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Holmberg, Jonas
    Swerea IVF AB, Mölndal, Sweden.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Understanding the effect of material composition and microstructural design on the erosion behavior of plasma sprayed thermal barrier coatings2019Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 488, s. 170-184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 37.
    Mahade, Satyapal
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Zhou, Dapeng
    Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Germany.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Vassen, Robert
    Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Germany.
    Tailored microstructures of gadolinium zirconate/YSZ multi-layered thermal barrier coatings produced by suspension plasma spray: Durability and erosion testing2019Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 264, s. 283-294Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 38.
    Markocsan, Nicolaie
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Manitsas, Dimosthenis
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Nicholas, Curry
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    MAX-phase coatings produced by thermal spraying2016Ingår i: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a comparative study on Ti2AlC coatings produced by different thermal spray methods, as Ti2AlC is one of the most studied materials from the MAX phase family. Microstructural analysis on coatings produced by High Velocity Air Fuel (HVAF), Cold Spray and High Velocity Oxygen Fuel (HVOF) has been carried out by means of scanning electron microscopy equipped with energy dispersive spectrometer (EDS). The volume fraction of porosity was determined using the ASTM standard E562. The phase characterization of the as-received powder and the as-sprayed coatings was conducted using X-ray diffraction with Cr Kα radiation. Impact of spray parameters on the porosity and the mechanical properties of the coatings are also discussed. The results show that the spraying temperature and velocity plays a crucial role on coatings characteristics.

  • 39.
    Medricky, Jan
    et al.
    Czech Technical University in Prague, Prague, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Pala, Zdenek
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Vilemova, Monika
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Chraska, Tomas
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Johansson, Jimmy
    GKN Aerospace Engine Systems, Trollhättan, Darrasa, Sweden.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former2015Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, nr 4, s. 622-628Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

  • 40.
    Musalek, Radek
    et al.
    Department of Materials Engineering, Institute of Plasma Physics AS CR, v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Fatigue Performance of TBC on Structural Steel Exposed to Cyclic Bending2014Ingår i: Proceedings of the International Thermal Spray Conference, ASM International, 2014, s. 880-885Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 41.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering , v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Fatigue Testing of TBC on Structural Steel by Cyclic Bending2015Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, nr 1-2, s. 168-174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 42.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Kovarik, Ondrej
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Pala, Zdenek
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Hausild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Materials.
    Capek, Jiri
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Solid State Engineering.
    Kolarik, Kamil
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Solid State Engineering.
    Nicholas, Curry
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Fatigue Performance of TBCs on Hastelloy X Substrate During Cyclic Bending2016Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, nr 1-2, s. 231-243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 43.
    Musalek, Radek
    et al.
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Pala, Zdenek
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Prague, Czech Republic.
    Tomek, Libor
    Czech Technical University in Prague, Prague, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Björklund, Stefan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Fatigue performance of TBCs on hastelioy X substrate during cyclic bending2015Ingår i: Thermal Spray 2015: Proceedings from the International Thermal Spray Conference (May 11–14, 2015, Long Beach, California, USA) / [ed] Agarwal A.,Lau Y.-C.,McDonald A.,Bolelli G.,Toma F.-L.,Concustell A.,Widener C.A.,Turunen, ASM International, 2015, Vol. 1, s. 406-412Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 44.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, V.v.i., Za Slovankou 3, 182 00 Praha, Czech Republic .
    Taltavull, Catalina
    Universidad Rey Juan Carlos, ESCET, 28933 Mostoles, Madrid, Spain .
    Lopez Galisteo, Antonio
    Universidad Rey Juan Carlos, ESCET, 28933 Mostoles, Madrid, Spain .
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Evaluation of failure micromechanisms of advanced thermal spray coatings by in-situ experiment2014Ingår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 606, s. 187-190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Identification of failure mechanisms of thermal spray coatings by means of traditional fractography of failed parts is often troublesome. The reason for this is a highly inhomogeneous character of the coating microstructure and harsh in-service conditions which may obscure evidentiary fractographic marks. In this study, failure evolution of advanced thermal barrier coating (TBC) prepared by plasma spraying was studied in-situ at high magnification in a scanning electron microscope under well-defined laboratory conditions of three-point bending (3PB). © (2014) Trans Tech Publications, Switzerland.

  • 45.
    Mušálek, Radek
    et al.
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Bertolissi, Gabriele
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Materials, .
    Kotlan, Jiří
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Pala, Zdenek
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Feasibility of suspension spraying of yttria-stabilized zirconia with water-stabilized plasma torch2015Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, nr April, s. 58-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal spraying of suspensions allows preparation of coatings from submicron-sized powders but demands a source of heat with a high enthalpy in order to provide an appropriate thermal treatment of the liquid feedstock during the in-flight stage so that the solvent may be evaporated, dispersed particles melted and accelerated towards the substrate to form a coating. Water-stabilized plasma (WSP) torch developed at the Institute of Plasma Physics AS CR, v.v.i. provides such a heat source with high enthalpy, high velocity of the plasma and, when compared to high-enthalpy gas-stabilized plasma (GSP) torches, relatively cheap operation. In this study, results of our experiments with suspension spraying of yttria-stabilized zirconia (YSZ) with WSP torch are presented and demonstrate that coating deposition with a high feed rate is possible with WSP technology. Formation of both columnar “cauliflower” microstructure and segmentation cracks was achieved. Variation of the deposition conditions was observed to modify coating microstructure in terms of splat morphology, porosity and thickness per pass, which is promising for further coating development.

  • 46.
    Tano, Ingrid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för maskinteknik och naturvetenskap.
    Nylen, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Wigren, Jan
    Gupta, Mohit Kumar
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Relationships between Coating Microstructure and Thermal Conductivity in Thermal Barrier Coatings – A modelling Approach2010Ingår i: International Thermal Spray Conference and Exposition, ITCS Singapore 2010: 3-5 May 2010,  Singapore, Düsseldorft: DVS Media , 2010, s. 66-72Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 47.
    Zou, Zhonghua
    et al.
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai 200240, China .
    Donoghue, Jack
    University of Manchester, School of Materials, Grosvenor Street, Manchester M1 7HS, UK .
    Curry, Nicholas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
    Yang, Lixia
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai 200240, China .
    Guo, Fangwei
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai 200240, China .
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Zhao, Xiaofeng
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai 200240, China .
    Xiao, Ping
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai 200240, China .
    A comparative study on the performance of suspension plasma sprayed thermal barrier coatings with different bond coat systems2015Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 275, s. 276-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of suspension plasma sprayed (SPS) yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) after isothermal treatment at 1150. °C was investigated. The NiCoCrAlY bond coats were applied by air plasma spray (APS) and high velocity oxygen fuel (HVOF) techniques. It was found that the microstructure of SPS TBCs depends on the surface morphology of the bond coat. The SPS TBCs with a rough APS bond coat exhibited a longer lifetime than those with a smooth HVOF bond coat. To understand this phenomenon, the evolution of the microstructure, mechanical properties and the residual stresses in the TBCs and TGO were systematically studied. Results showed that the surface roughness and oxidation behavior of the bond coat play dominant roles in the SPS TBC failure. © 2015.

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