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  • 1.
    Abou Nada, Fahed
    et al.
    Lund University, Department of Physics, Division of Combustion Physics, Box 118, Lund, Swede.
    Lantz, Andreas
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Larfeldt, Jenny
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Alden, Marcus
    Lund University, Department of Physics, Division of Combustion Physics, Box 118, Lund, Swede.
    Richter, Mattias
    Lund University, Department of Physics, Division of Combustion Physics, Box 118, Lund, Swede.
    Remote temperature sensing on and beneath atmospheric plasma sprayed thermal barrier coatings using thermographic phosphors2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 302, p. 359-367Article in journal (Refereed)
    Abstract [en]

    Investigations on remote temperature sensing of yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) at the surface and at the bond-coat/top-coat interface were carried out. Using Y2O3:Eu thermographic phosphor as an embedded temperature sensing layer, sub-surface temperature probing through 300 mu m of atmospheric plasma sprayed YSZ is demonstrated. The Y2O3:Eu thermographic phosphor displays a temperature sensitivity ranging between 400 degrees C up to a maximum of 900 degrees C when utilizing the luminescence originating from the 611 nm emission band. Dysprosium stabilized zirconia (10 wt.% DySZ), a TBC material, is also investigated and established as a temperature sensor from 400 degrees C up to a temperature of 1000 degrees C using both the intensity decay time and emission intensity ratio methods. In addition, the luminescence of presumed optically inactive YSZ materials was spectroscopically investigated in terms of optical interferences caused by impurities. A validation temperature probing measurement through 300 mu m of YSZ top-coat was successfully performed in a SGT-800 Siemens burner running at six different operating conditions in an atmospheric combustion rig. (C) 2016 Elsevier B.V. All rights reserved.

  • 2.
    Algenaid, Wael
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ganvir, Ashish
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Calinas, Rosa Filomena
    Innovnano materials, Coimbra, Portugal.
    Varghese, Johny
    University of Hyderabad, Hyderabad, India.
    Rajulapati, Koteswararao V.
    University of Hyderabad, Hyderabad, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Influence of microstructure on the erosion behaviour of suspension plasma sprayed thermal barrier coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 375, p. 86-99Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) are applied on the surface of hot parts of gas turbine engines to increase the turbine efficiency by providing thermal insulation and to protect the engine parts from the harsh environment. Typical degradation of TBCs can be attributed to bond coat oxidation, thermal stress etc. In addition to this, erosion can also lead to partial or complete removal of the TBCs especially when the engine operates under erosive environment such as flying over desert area, near active volcanic or offshore ocean environment. Suspension Plasma Spraying (SPS) is a promising technique for TBC applications by virtue of its ability to produce a strain-tolerant porous-columnar microstructure that combines the benefits of both electron beam physical vapor deposited (EB-PVD) as well as atmospheric plasma sprayed (APS) coatings. This work investigates the influence of various coating microstructures produced by SPS on their erosion behavior. Six different coatings with varied microstructures produced using different suspensions with distinct characteristics were studied and their erosion resistance was compared. Results showed significant influence of SPS TBCs microstructures on the erosion resistance. Furthermore, the erosion resistance of SPS TBCs showed a close correlation between fracture toughness and the erosion rate, higher fracture toughness favours superior erosion resistance. © 2019 Elsevier B.V.

  • 3.
    Chen, Ying
    et al.
    University of Manchester,School of Materials, M13 9PL, Manchester, United Kingdom.
    Zhang, Xun
    University of Manchester,School of Materials, M13 9PL, Manchester, United Kingdom.
    Zhao, Xiaofeng
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, Shanghai, 200240, China.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Xiao, Ping
    University of Manchester,School of Materials, M13 9PL, Manchester, United Kingdom; Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, Shanghai, 200240, China.
    Measurements of elastic modulus and fracture toughness of an air plasma sprayed thermal barrier coating using micro-cantilever bending2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 374, p. 12-20Article in journal (Refereed)
    Abstract [en]

    The elastic modulus and fracture toughness of an air plasma sprayed thermal barrier coating (APS TBC) were measured using the micro-cantilever bending technique. The micro-cantilevers were machined by a focused ion beam with their central arms either parallel or normal to the bond coat/topcoat interface. Such orientations allowed direct measurements of both the in-plane and out-of-plane elastic moduli as well as mode I fracture toughness by bending. The calculated elastic modulus along the in-plane and out-of-plane direction is 144 GPa and 110 GPa, respectively, suggesting that the APS TBC is elastically anisotropic at microscale. The derived mode I fracture toughness along the plane parallel to the interface is 0.40 MPam. This relatively low toughness reflects the weak fracture resistance of the highly-flawed APS for short cracks at microscale. The measurements in this study can be incorporated into micromechanical life time prediction models of the APS TBCs. © 2019 Elsevier B.V.

  • 4.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science.
    Donoghue, Jack
    University of Manchester.
    Evolution of thermal conductivity of dysprosia stabilised thermal barrier coating systems during heat treatment2012In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, ISSN 0257-8972, Vol. 209, p. 38-43Article in journal (Refereed)
    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.

  • 5.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Tang, Zhaolin
    Northwest Mettech Corp., Vancouver, Canada.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of Bond Coat Surface Roughness on the Structure of Axial Suspension Plasma Spray Thermal Barrier Coatings - Thermal and Lifetime Performance2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, no April, p. 15-23Article in journal (Refereed)
  • 6.
    Frodelius, Jenny
    et al.
    Linköping University, Thin Film Physics Division, Department of Physics.
    Sonestedt, Marie
    Chalmers University of Technology, Microscopy and Microanalysis, Department of Applied Physics.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Palmquist, Jens-Petter
    Kanthal AB, 734 27 Hallstahammar, Sweden.
    Stiller, Krystyna
    Chalmers University of Technology, Microscopy and Microanalysis, Department of Applied Physics.
    Högberg, Hans
    Linköping University, Thin Film Physics Division, Department of Physics.
    Hultman, Lars
    Linköping University, Thin Film Physics Division, Department of Physics.
    Ti2AlC coatings deposited by High Velocity Oxy-Fuel spraying2008In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 24, p. 5976-5981Article in journal (Refereed)
    Abstract [en]

    High Velocity Oxy-Fuel has been utilized to spray coatings from Ti2AlC (MAXTHAL 211®) powders. X-ray diffraction showed that the coatings consist predominantly of Ti2AlC with inclusions of the phases Ti3AlC2, TiC, and Al–Ti alloys. The fraction of Ti2AlC in coatings sprayed with a powder size of 38 μm was found to increase with decreasing power of the spraying flame as controlled by the total gas flow of H2 and O2. A more coarse powder (56 μm) is less sensitive to the total gas flow and retains higher volume fraction of MAX-phase in the coatings, however, at the expense of increasing porosity. X-ray pole figure measurements showed a preferred crystal orientation in the coatings with the Ti2AlC (000l) planes aligned to the substrate surface. Bending tests show a good adhesion to stainless steel substrates and indentation yields a hardness of 3–5 GPa for the coatings sprayed with a powder size of 38 μm.

  • 7.
    Goel, Sneha
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Ind AG, Althofen, Austria.
    Wiklund, U.
    Uppsala Univ, Dept Technol, Mat Sci Div, S-75121 Uppsala, Swede.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Axial suspension plasma spraying of Al2O3 coatings for superior tribological properties2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 315, p. 80-87Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spray is a relatively new thermal spray technique which enables feeding of fine powder to produce advanced coatings for varied applications. This work investigates the difference in structure and performance of Al2O3 coatings manufactured using conventional micron-sized powder feedstock and a suspension of sub-micron to few micron sized powder. Axial injection was implemented for deposition in both cases. The effect of feedstock size and processing on the tribological performance of the two coatings was of specific interest. The coatings were characterized by Optical and Scanning Electron Microscopy, micro-hardness and scratch resistance testing, and their dry sliding wear performance evaluated. The suspension sprayed coatings yielded significantly higher scratch resistance, lower friction coefficient and reduced wear rate compared to conventional coatings. The improved tribological behaviour of the former is attributable to finer porosity, smaller splat sizes, and improved interlamellar bonding. (C) 2017 Elsevier B.V. All rights reserved.

  • 8.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eriksson, Robert
    Linköping University, Linköping, Sweden.
    Sand, Ulf
    EDR Medeso, Västerås, Sweden.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    A Diffusion-based Oxide Layer Growth Model using Real Interface Roughness in Thermal Barrier Coatings for Lifetime Assessment2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 271, no June, p. 181-191Article in journal (Refereed)
    Abstract [en]

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

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

  • 9.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Turbomachinery AB, Finspång, Sweden.
    Kjellman, Björn
    GKN Aerospace, Trollhättan, Sweden.
    Development of bondcoats for high lifetime suspension plasma sprayed thermal barrier coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no SI, p. 366-377Article in journal (Refereed)
    Abstract [en]

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

  • 10.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Peng, Ru Lin
    Linköping University, Linköping, Sweden.
    Improving the lifetime of suspension plasma sprayed thermal barrier coatings2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 550-559Article in journal (Refereed)
    Abstract [en]

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

  • 11.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Weber, André
    Karlsruhe Institute of Technology, Germany.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Helden, Nadine
    Oerlikon Metco, Germany.
    Development of plasma sprayed Ni/YSZ anodes for metal supported solidoxide fuel cells2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 178-189Article in journal (Refereed)
    Abstract [en]

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

  • 12. Kumar, M.
    et al.
    Singh, H.
    Singh, N.
    Hong, S. M.
    Choi, I. S.
    Suh, J. Y.
    Chavan, N. M.
    Kumar, S.
    Joshi, S. V.
    Development of nano-crystalline cold sprayed Ni-20Cr coatings for high temperature oxidation resistance2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 266, p. 122-133Article in journal (Refereed)
    Abstract [en]

    In the current investigation a pre-synthesized nano-crystalline Ni-20Cr powder was deposited by cold-spray technique on SA 516 steel. The powder was synthesized by ball milling approach. The nano-crystallinity of the developed coating was established by crystallite size measurements from XRD profile, which was further endorsed by TEM analysis. High-temperature oxidation behavior of uncoated and coated samples was studied under cyclic isothermal conditions at 900 degrees C for 50 cycles in a laboratory tube furnace. The oxidation rates for the bare and coated steel were evaluated in terms of weight gain data. Different characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and transmission electron microscopy (TEM) analyses were utilized to characterize the oxide scale. The hardness and oxidation resistance of the steel increased after the application of coating. The reduction in oxidation rate of the base steel was 94%. Moreover, the developed nanostructured coating was observed to reduce weight gain by 64% in comparison with micron-sized Ni-20Cr cold spray coating thus offers a higher oxidation resistance. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the nanostructured coating. (C) 2015 Elsevier B.V. All rights reserved.

  • 13.
    Kumar, S.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur.Po, Hyderabad 500 005, India.
    Jyothirmayi, A.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur.Po, Hyderabad 500 005, India.
    Wasekar, Nitin
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur.Po, Hyderabad 500 005, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Influence of annealing on mechanical and electrochemical properties of cold sprayed niobium coatings2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 296, p. 124-135Article in journal (Refereed)
    Abstract [en]

    Abstract In the present study, thick and dense niobium coatings were obtained using cold spray technique by using air as a process gas. Inter-splat boundaries are completely removed in the coatings heat treated at 1500 °C by the formation of equiaxed grains. Heat treatment reduces the porosity level to 0.1%. Inter-splat boundary bonding state of the heat treated coatings was investigated using micro-tensile testing, scratch testing and nanoindentation and compared with the bulk niobium. The elastic modulus of the cold spray coatings heat treated at 1500 °C exhibits as high as 103 GPa whereas the same for bulk is 105 GPa. The increase in mechanical strength of inter-splat boundary from as-sprayed condition to 1500 °C was estimated to be 750%. Similarly corrosion performance of heat treated coatings was also evaluated in 1 M KOH solution through potentiodynamic polarization as well as impedance spectroscopy studies. The corrosion rate for the coatings heat treated at 1500 °C was estimated to be 0.443 MPY which is comparable for the bulk (0.498 MPY). Coatings annealed at 1250 °C and above, which is very close to the recrystallization temperature of niobium, were found to perform almost as bulk niobium indicating exciting implications for various applications. Assessment of structure–property correlations was done based on the microstructure, porosity and inter-splat bonding state, together with the mechanical and corrosion properties of the heat treated tantalum cold sprayed coatings.

  • 14.
    Kumar, S.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Reddy, S.K.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructure and performance of cold sprayed Al-SiC composite coatings with high fraction of particulates2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 62-71Article in journal (Refereed)
    Abstract [en]

    Deposition of metal matrix composites (MMCs) through thermal spraying has traditionally presented problems associated with heterogeneity, porosity, and low wettability of particulates with matrix. Cold spray is a very rapid deposition process which is suitable for depositing a variety of ductile materials without any thermal degradation. Many researchers have attempted to deposit Al-SiC MMCs with 10–20% SiC using this technique. In the present study, three different powder compositions (FAl-23SiC, FAl-46SiC, FAl-71SiC) obtained by mixing Al and SiC powders were cold sprayed on aluminum substrates. The volume percentage and the average size of the SiC particulates in the cold sprayed coatings were estimated and found to be 23%, 47% and 52% for FAl-23SiC, FAl-46SiC and FAl-71SiC feedstocks, respectively. Effects of percentage and size of the SiC particulate retained in the composite coatings on the mechanical properties and the sliding wear performance were studied at different sliding conditions in the as-sprayed and heat treated conditions. The results were comprehensively analyzed and found to correlate well with the microstructure of the coatings.

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

    Replacement of Electrolytic Hard Chromium (EHC) method by Thermal Spray Technology has shown a growing interest the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly-developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, a first order process map has been intended via a full factorial Design of Experiments (DoE) to establish relationships between powder feedstock characteristics, such as primary carbides grain size, binder grain size and powder strength, and coatings microstructure and mechanical properties. A second order process map was then established to study possible correlations between the deposit microstructural properties and their respective abrasion/erosion wear and corrosion performances.

  • 16.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Thermal conductivity and thermal cyclic fatigue of multilayered Gd2Zr2O7/YSZ thermal barrier coatings processed by suspension plasma spray2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 283, p. 329-336Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Vassen, Robert
    Forschungszentrum Julich, Inst Energy & Climate Res IEK 1, Julich, German.
    Functional performance of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings deposited by suspension plasma spray2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 208-216Article in journal (Refereed)
    Abstract [en]

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

  • 18.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Jonnalagadda, Krishna Praveen
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 357, p. 456-465Article in journal (Refereed)
    Abstract [en]

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

  • 19.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Jonnalagadda, Krishna Praveen
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Engineered architectures of gadolinium zirconate based thermal barrier coatings subjected to hot corrosion test2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 328, p. 361-370Article in journal (Refereed)
    Abstract [en]

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

  • 20.
    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
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Feasibility of suspension spraying of yttria-stabilized zirconia with water-stabilized plasma torch2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, no April, p. 58-62Article in journal (Refereed)
    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.

  • 21. Pulugurtha, S. R.
    et al.
    Bhat, D. G.
    Gordon, M. H.
    Shultz, J.
    Staia, M.
    Joshi, S. V.
    Govindarajan, S.
    Mechanical and tribological properties of compositionally graded CrAlN films deposited by AC reactive magnetron sputtering2007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 4-7, p. 1160-1166Article in journal (Refereed)
    Abstract [en]

    In this work, CrAlN films with Al/Cr atomic ratios between 0.02 and 1.4 were deposited on tool inserts by AC magnetron sputtering at 5 kW for three different Ar/N-2 flow rates. The unique configuration of the inverted cylindrical magnetron sputtering (ICM-10) system enables the deposition of compositionally graded Cr-Al-N coatings under a single deposition condition. The effect of aluminum on the structural, mechanical and tribological properties of (CrAl)N coatings are reported and compared with ALCRONA and CrN coatings from Balzers. Mechanical properties have been evaluated by the microhardness indentation technique, and the hardness is 18 and 15 GPa for CrN and CrAlN films, respectively. The tribological tests have been performed using the pin-on-disc method at room temperature and 700 degrees C. The results indicate that the coefficient of friction at room temperature and 700 degrees C for all the deposited coatings, Balzers-ALCRONA and CrN fall between 0.4-0.6. The wear volume at high temperature (700 degrees C) decreases with increase in Al incorporation. Auger Electron Spectroscopy reveals that all films have about 10 at.% of oxygen. Atomic Force Microscopy showed that our films had roughness ranging from 80 to 150 nm. X-ray mapping on (Cr, Al)N coatings for different Ar/N-2 gas compositions showed transitions from cubic to hexagonal with decreasing nitrogen. (0 2007 Elsevier B.V. All rights reserved.

  • 22. Rajasekaran, B.
    et al.
    Raman, S. G. S.
    Joshi, S. V.
    Sundararajan, G.
    Effect of detonation gun sprayed Cu-Ni-In coating on plain fatigue and fretting fatigue behaviour of Al-Mg-Si alloy2006In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 201, no 3-4, p. 1548-1558Article in journal (Refereed)
    Abstract [en]

    Detonation gun spray technique was employed to coat Al-Mg-Si alloy (AA 6063) specimens with Cu-Ni-In powder. Coated samples were characterized with reference to the microstructure, porosity, residual stresses, microhardness and surface roughness. Plain fatigue (without fretting) and fretting fatigue tests were carried out at room temperature on uncoated and coated specimens. The detonation gun spray process resulted in a dense coating of almost uniform deposition with low porosity (0.3%) and good adhesion between the substrate and the coating. Under plain fatigue loading 40 mu m thick coated samples exhibited superior lives compared with uncoated and 100 mu m thick coated specimens due to the presence of higher surface compressive residual stress in the former. Delamination-induced failure resulted in inferior lives of 100 mu m thick coated specimens. Under fretting fatigue deformation 40 mu m thick coated specimens exhibited superior lives compared with 100 mu m thick coated samples owing to higher compressive residual stress at the surface and better interfacial adhesion. At 120 MPa stress level 40 pm thick coated specimens exhibited superior fretting fatigue life compared with uncoated sample and at stress levels above 120 MPa the converse was true. This was attributed to interface cracking at higher stress levels. (c) 2006 Elsevier B.V. All rights reserved.

  • 23.
    Sadeghi, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Chlorine-induced high-temperature corrosion and erosion-corrosion of HVAF and HVOF-sprayed amorphous Fe-based coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no S1, p. 20-35Article in journal (Refereed)
    Abstract [en]

    Chlorine-induced high-temperature corrosion and erosion-corrosion behavior of amorphous Fe-based coatings sprayed by high velocity air-fuel (HVAF) and high velocity oxy-fuel (HVOF) techniques were investigated. The coated specimens were first exposed to isothermal high-temperature corrosion at 600 °C in ambient air with and without KCl. The exposed specimens were then subjected to alumina erodent. The as-sprayed HVAF coating showed a more compact and uniform microstructure with a higher hardness leading to higher corrosion and erosion-corrosion resistance. After erosion, all the coatings similarly exhibited a combined brittle/ductile damage to surface oxide scale that previously formed in the corrosive environment. The corrosion and erosion-corrosion behavior of the coatings primarily relied on the uniformity of coatings’ microstructure and distribution of alloying elements to form the protective oxide scale in the corrosive environment, which can resist against erodent in the erosive media. © 2019 Elsevier B.V.

  • 24.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Huhtakangas, M.b
    M. H. Engineering AB, 691 42 Karlskoga, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Isothermal oxidation of HVAF-sprayed Ni-based chromia, alumina and mixed-oxide scale forming coatings in ambient air2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 316, p. 10-21Article in journal (Refereed)
    Abstract [en]

    The power generation industry has been progressively shifting towards higher operating steam temperatures and pressures to increase efficiency and reduce CO2 emissions. However, higher operating temperatures lead to more aggressive oxidation of the boiler components. A promising route to improve the durability of degradation-prone components is through deployment of high-performance coatings. In the present work, four Ni-based coatings - Ni21Cr, Ni5Al, Ni21Cr9Mo, and Ni21Cr7Al1Y - thermally sprayed by the high-velocity air fuel (HVAF) technique on boiler steel (16Mo3) substrates were investigated. The isothermal oxidation behavior of the coatings was studied in ambient air environment at 600 °C for different time intervals i.e. 1, 5, 10, 24, 48, 96, and 168 h. The oxidation behavior of the as-sprayed and polished coatings was compared. The protective α-Al2O3 was not detected on the exposed alumina-forming NiAl coating. On the other hand, Cr2O3 along with a small amount of NiO were the main oxidation products on the surface of the NiCr and NiCrMo coatings, and were found to be relatively less protective. The mixed-oxide scale forming NiCrAlY coatings showed the best oxidation resistance due to the formation of a thin and slow-growing Al2O3 scale along with Ni(Al,Cr)2O4 and Cr2O3. The polished coatings were found to significantly reduce the oxidation rate in each case as the protective scale-forming elements were more uniformly supplied to the surface oxide scale by removing the surface asperities. © 2017 Elsevier B.V.

  • 25.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Isothermal oxidation behavior of HVAF-sprayed Ni and NiCr coatings in H2-H2O environment2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 317, p. 17-25Article in journal (Refereed)
    Abstract [en]

    The formation of a protective chromia scale on stainless steels is known to be suppressed by the presence of water vapor in reducing conditions. Thermal spray coatings present a promising approach to improve the durability of steels by transferring the first line of oxidation attack from the bulk steel to the coating. In the present work, isothermal oxidation behavior of Ni and NiCr coatings deposited by High-Velocity Air Fuel (HVAF) process on 304L stainless steel was investigated at 600 degrees C for 168 h. Ar-10%H-2-20%H2O was selected as the oxidation environment to study the oxidation behavior of the coatings in a low pO(2) environment containing H2 and H2O. BIB/ SEM, EDS, and XRD techniques were used to characterize the as-sprayed coatings and to investigate the oxidation mechanisms in the coated samples. Results showed that both Ni and NiCr coatings imparted oxidation protection to the 304L substrate. The chromia-forming 304L steel presented a duplex but non-protective oxide scale comprising of an outer Fe3O4 layer on an inner (Fe, Cr)(3)O-4-spinel oxide. In contrast, the NiCr coating presented superior oxidation behavior due to the formation of a continuous, thin, and slow-growing Cr2O3 scale. The Ni coating, too, protected the substrate owing to limited nucleation and growth of the deleterious NiO scale in the low-oxygen -activity environment. (C) 2017 Elsevier B.V. All rights reserved.

  • 26.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylen, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructural characteristics and corrosion behavior of HVAF- and HVOF-sprayed Fe-based coatings2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 365-373Article in journal (Refereed)
    Abstract [en]

    Fe-based coatings have been shown to be viable alternatives to the more expensive and less environmentally friendly Co- and Ni-based coatings. In the present work, the microstructural characteristics and corrosion behavior of Fe-based coatings deposited by high-velocity air fuel (HVAF) and high-velocity oxy fuel (HVOF) processes were comparatively investigated. Different sets of powder composition and particle size were used to decrease the porosity and increase the corrosion resistance of the coatings. The corrosion behavior of the coatings was studied using electrochemical techniques, including open-circuit potential (OCP) and polarization tests in 3.5 wt% NaCl at 25 °C. Techniques such as scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffractometry (XRD) were used to characterize the as-sprayed and corroded coatings. The results revealed that the HVAF coatings had lower porosity and oxide content than the HVOF coatings. The polarization tests confirmed that the HVAF coatings sprayed with finer particle size (− 36 + 20 μm) have higher polarization resistance (Rp) than the coatings produced by powders (− 53 + 20 μm). Based on SEM analysis, it was observed that corrosion initiated and grew through the surface defects of the coating and propagated through inter-lamellar boundaries.

    Keywords

  • 27.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructural and electrochemical characterization of Ni-based bi-layer coatings produced by the HVAF process2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 304, p. 606-619Article in journal (Refereed)
    Abstract [en]

    Bi-layer coating systems comprising a Cr3C2-NiCr coating with different underlying coatings of Ni, NiCr, NiCoCrAlY, and CoNiCrAlY were deposited on 304L stainless steel substrates using the high-velocity air fuel (HVAF) process. The corrosion behavior of the coating systems was studied using electrochemical and immersion tests in 3.5 wt% NaCl at 25 °C. The higher open-circuit potential (OCP) value of the NiCoCrAlY coating (− 120 mV/SCE) compared to the value of the Cr3C2-NiCr coating (− 230 mV/SCE) revealed that the underlying NiCoCrAlY coating was sacrificially protected by Cr3C2-NiCr coating. The polarization resistance (Rp) of the bi-layer coatings with the different underlying coatings of Ni, NiCr, NiCoCrAlY and CoNiCrAlY was approximately 77, 189, 487, and 74 kΩ·cm2 respectively, while the value was 101 kΩ·cm2 for the single-layer Cr3C2-NiCr coating and 30 kΩ·cm2 for the 304L substrate, which confirmed a higher corrosion protection of the NiCoCrAlY coating. The electrochemical impedance spectroscopy (EIS) results showed that the corrosion resistance of the 304L substrate was significantly improved by adding an intermediate layer of NiCoCrAlY to the Cr3C2-NiCr coating. Results of the immersion tests confirmed that the underlying coatings in the different bi-layer coating systems acted as protective barriers. Moreover, the NiCoCrAlY coating showed the best corrosion protection among the investigated underlying coatings.

  • 28. Shariff, S. M.
    et al.
    Pal, T. K.
    Padmanabham, G.
    Joshi, S.
    Influence of chemical composition and prior microstructure on diode laser hardening of railroad steels2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 228, p. 14-26Article in journal (Refereed)
    Abstract [en]

    Diode laser surface treatment of three different railroad steels, namely pearlitic railroad-rail steel (PRS), ferritic-pearlitic railroad-wheel steel (FPRS) and bainitic railroad-rail steel (BRS), has been investigated. Power-ramping experiments, with in-situ surface temperature measurement, were initially carried out to assess surface temperature effects on treated layers. Influence of laser energy on characteristics of treated layers like surface topology, case-depth, microstructure and micro-hardness was comprehensively analyzed. Results revealed that the hardened layer depth is governed by both the process parameters as well as the nature of the substrate steel. With melting, significant reduction in hardness was noted owing to an increase in residual austenite and coarsening of martensitic microstructure. Unlubricated dry-sliding wear tests performed under close to real rail/wheel conditions revealed substantial improvement in wear resistance of hardened/melted rail steels compared to the parent substrates. The observed differences in characteristics of the laser-treated layers and their tribological behavior have been correlated with the chemistry and prior microstructure of the parent substrates. (C) 2013 Elsevier B.V. All rights reserved.

  • 29.
    Silveira, L. L.
    et al.
    UTFPR – Universidade Tecnológica Federal do Paraná, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR 84016-210, Brazil.
    Pukasiewicz, A. G. M.
    UTFPR – Universidade Tecnológica Federal do Paraná, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR 84016-210, Brazil.
    de Aguiar, D. J. M.
    UTFPR – Universidade Tecnológica Federal do Paraná, Post-graduate Program in Mechanical Engineering, Ponta Grossa, PR 84016-210, Brazil.
    Zara, A. J.
    UEPG – Universidade Estadual de Ponta Grossa, Ponta Grossa, PR 84010-330, Brazil.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Study of the corrosion and cavitation resistance of HVOF and HVAF FeCrMnSiNi and FeCrMnSiB coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 374, p. 910-922Article in journal (Refereed)
    Abstract [en]

    Cavitation and corrosion on hydrodynamic components and systems reduces the operational efficiency. The use of wear resistant coatings has been studied as a solution to the problem of corrosion and cavitation in industrial environments. The high velocity oxy-fuel process (HVOF) can produce coatings with high density and bond strength. High velocity air-fuel (HVAF) is an alternative process, which can deposit coatings with higher velocity and lower temperatures, compared to the HVOF process, resulting in lower oxide content. This paper analyzes the HVOF and HVAF processes to deposit FeCrMnSiNi and FeCrMnSiB coatings, comparing their cavitation and corrosion resistance. HVAF coatings presented lower porosity and oxide levels, as well as higher hardness values. The HVAF process presented better cavitation and corrosion resistance, due to lower porosity and oxide contents of the coatings. The amount of oxides and pores in the coatings was crucial in their corrosive behavior, by facilitating the penetration of the chloride ions through the pores, leading to a higher corrosion rate and pitting formation. © 2019 Elsevier B.V.

  • 30.
    Sivakumar, G.
    et al.
    Center for Engineered Coatings, International Advanced Research Center for Powder Metallurgy and New Materials, Hyderabad, India.
    Banerjee, S.
    Indian Institute of Technology Bombay, Department of Metallurgical Engineering and Materials Science, Mumbai, India.
    Raja, V. S.
    Indian Institute of Technology Bombay, Department of Metallurgical Engineering and Materials Science, Mumbai, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Hot corrosion behavior of plasma sprayed powder-solution precursor hybrid thermal barrier coatings2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 349, p. 452-461Article in journal (Refereed)
    Abstract [en]

    In recent times, plasma sprayed powder-solution precursor hybrid composite thermal barrier coatings have been developed to harness the dual benefits of both conventional atmospheric plasma spraying (APS) and solution precursor plasma spraying (SPPS) processes. In this study, hot corrosion behavior of plasma sprayed powder-solution precursor composite (PSP-SPC) YSZ TBCs in molten salt mixtures of 90 wt.% Na2SO4 + 5 wt.% V2O5 + 5 wt.% NaCl and 50 wt.% Na2SO4 + 50 wt.% V2O5 at 900 °C was investigated. The employed coating showed a bimodal microstructure comprising coarse splats derived from the powder feedstock as in the APS process and fine splats resulting from the solution precursor as typical of SPPS process. The PSP-SPC coatings showed a significantly higher resistance to spallation than APS, SPPS and EB-PVD coatings in both the salt environments. These coatings showed shorter life in vanadate environment compared to that of the chloride environments as the former promotes the formation of monoclinic ZrO2 and YVO4 phases more than the latter. © 2018

  • 31.
    Sokolowski, Pawel
    et al.
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Musalek, Radek
    Inst Plasma Phys CAS, Dept Mat Engn, Vvi, Slovankou 3, Prague 18200, Czech Republi.
    Candidato, Rolando T. Jr.
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, France.
    Pawlowski, Lech
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Nait-Ali, Benoit
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Smith, David
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, Fran.
    Thermophysical properties of YSZ and YCeSZ suspension plasma sprayed coatings having different microstructures2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 28-38Article in journal (Refereed)
    Abstract [en]

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

  • 32.
    Sokolowski, Pawel
    et al.
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Musalek, Radek
    Inst Plasma Phys CAS, Vvi, Dept Mat Engn, Slovankou 3, Prague 18200, Czech Republic.
    Latka, Leszek
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Kozerski, Stefan
    Wroclaw Univ Sci & Technol, Fac Mech Engn, Ul Lukasiewicza 5, PL-50371 Wroclaw, Poland.
    Dietrich, Dagmar
    Tech Univ Chemnitz, Inst Mat Sci & Engn, D-09107 Chemnitz, Germany.
    Lampke, Thomas
    Tech Univ Chemnitz, Inst Mat Sci & Engn, D-09107 Chemnitz, Germany.
    Pawlowski, Lech
    Univ Limoges, Lab SPCTS, UMR CNRS 7315, 12 Rue Atlantis, F-87068 Limoges, France.
    The microstructural studies of suspension plasma sprayed zirconia coatings with the use of high-energy plasma torches2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 250-261Article in journal (Refereed)
    Abstract [en]

    The presented studies are focused on the microstructure characterization of zirconia-based coatings deposited by two types of high-energy plasma torches: (i) Axial III; and, (ii) hybrid version of Water-Stabilized Plasma (WSP) torch. The suspensions were formulated using solid dispersed phase of: (i) zirconia stabilized with 14 wt of Y2O3 and (ii) zirconia stabilized with 24 wt% of CeO2 + 2.5 wt% of Y2O3 and continuous phase of water with ethanol. The spray process parameters were optimized for each plasma set-up individually. The in-flight observations (shadowgraphy) were performed to optimize the injection of the liquid feedstock into the plasma jet. Then the coating’s morphology and coating/substrate interface were characterized using conventional light microscopy and scanning electron microscopy (SEM). The results showed that through the change of deposition parameters various coatings microstructures could be obtained, in particular columnar and two-zones structures. The EDS/EDX and XRD studies showed that there was no significant change in chemical/phase composition of zirconia material before and after spraying. Electron backscatter diffraction (EBSD) method allowed to analyze the grain size in the coating microstructure as well as crystallographic orientation of individual grains. The results showed that coatings were characterized by submicrometric microstructure what corresponded to the size of powder particles used to formulate suspension. No texture was observed in the coatings microstructure. The surface topography analysis which was performed by confocal scanning laser microscopy (CSLM) and Shape From Shading (SFS) technique proved the great influence of suspension concentration on the coating structure. (C) 2017 Elsevier B.V. All rights reserved.

  • 33.
    Tesar, Tomas
    et al.
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic; Czech Technical University in Prague, Faculty of Nuclear Science and Physical Engineering, Department of Materials, Trojanova 13, 120 00 Praha 2, Czech Republic .
    Musalek, Radek
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Lukac, Frantisek
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Cizek, Jan
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Rimal, Vaclav
    Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Praha 8, Czech Republic.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Chraska, Tomas
    Institute of Plasma Physics CAS, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Praha 8, Czech Republic.
    Increasing α-phase content of alumina-chromia coatings deposited by suspension plasma spraying using hybrid and intermixed concepts2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no S1, p. 298-311Article in journal (Refereed)
    Abstract [en]

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

  • 34.
    Zhang, Pimin
    et al.
    Linköping University, Department of Management and Engineering, Linköping, SE-58183, Sweden.
    Sadeghi, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry, and Biology, Linköping, SE-58183, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, SE-61283, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry, and Biology, Linköping, SE-58183, Sweden.
    Buyanova, Irina A.
    Linköping University, Department of Physics, Chemistry, and Biology, Linköping, SE-58183, Sweden.
    Peng, Ru L.in
    Linköping University, Department of Management and Engineering, Linköping, SE-58183, Sweden.
    Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 364, p. 43-56Article in journal (Refereed)
    Abstract [en]

    Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

  • 35.
    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
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    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
    University West, Department of Engineering Science, Division of Production Engineering.
    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 systems2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 275, p. 276-282Article in journal (Refereed)
    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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