| 1. |
- Ganvir, Ashish, 1991-, et al.
(författare)
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Failure analysis of thermally cycled columnar thermal barrier coatings produced by high-velocity-air fuel and axial-suspension-plasma spraying : A design perspective
- 2018
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 44:3, s. 3161-3172
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Tidskriftsartikel (refereegranskat)abstract
- Axial-suspension-plasma spraying (ASPS) is a fairly recent thermal spray technology which enables production of ceramic top coats in TBCs, incorporating simultaneously the properties of both the conventional-plasma sprayed (highly insulating porous structures) and electron-beam-physical-vapor-deposited (strain-tolerant columnar structures) top coats. TBCs are required to insulate the hot components in a gas turbine engine against high temperature and harsh operating conditions. Periodic heating and cooling of turbine engines during operation can create severe thermal cyclic fatigue conditions which can degrade the performance of these coatings eventually leading to the failure. An in-depth experimental investigation was performed to understand the failure behavior of columnar TBCs subjected to thermal cyclic fatigue (TCF) test at 1100 C. The study revealed that the TCF performance was influenced to an extent, by the top coat microstructure, but was primarily affected by the severity of thermally grown oxide (TGO) growth at the bond coat-top coat interface. Mixed failure modes comprising crack propagation through the bond coat-TGO interface, through TGO and within the top coat were identified. Based on the analysis of the experimental results and thorough discussion a novel design of microstructure for the high TCF performance columnar TBC is proposed. © 2017 Elsevier Ltd and Techna Group S.r.l.
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| 2. |
- Mahade, Satyapal, 1987-, et al.
(författare)
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Influence of processing conditions on the microstructure and sliding wear of a promising Fe-based coating deposited by HVAF
- 2021
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 409, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- Thermal spray is a versatile and cost-effective process to deposit wear and corrosion resistant coatings. In this work, a relatively new ‘Fe-based’ chemistry comprising boride and carbides, is explored as a ‘greener’ alternative to the relatively expensive and carcinogenic Co-based coatings to mitigate wear. The emergent thermal spray process of high-velocity air-fuel (HVAF) spraying was chosen to deposit the Fe-based coatings, with the high-velocity oxy-fuel (HVOF) also being employed solely for the purpose of preliminary comparison. Detailed characterization of the HVOF and HVAF sprayed Fe-based coatings was carried out. Microstructure, porosity, hardness and phase analysis results demonstrate the influence of processing conditions, where specific spray conditions yielded minimal undeformed particulates content, high hardness, low porosity and feedstock phase retention. Differences in microstructural features of the as-deposited coatings in relation to their processing conditions are discussed in detail. The coatings were subjected to ball-on-disc tribometry tests at different load conditions and their friction and wear performance were evaluated. The coefficient of friction results of investigated coatings concurred with their respective microstructural features. Post-mortem of the worn coating surface, the mating alumina ball surface and wear debris was performed using SEM/EDS analysis to understand the associated wear mechanisms and material transfer. This work provides new insights on identifying appropriate HVAF processing conditions to achieve acceptable microstructural features and phases in Fe-based coatings for improved wear performance.
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| 3. |
- Mahade, Satyapal, 1987-, et al.
(författare)
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Sliding wear behavior of a sustainable Fe-based coating and its damage mechanisms
- 2022
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 500-501
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Tidskriftsartikel (refereegranskat)abstract
- The current industry demand is to identify suitable alternatives to the risk-of-supply prone and/or toxic, WC-Co and electrolytic hard chrome coatings without comprising the desired wear performance. Therefore, compositions based on abundantly available elements (e.g. ‘Fe’) that possess adequate wear resistance are desirable from health, sustainability and economic standpoints. In this work, crystalline Fe-based (Rockit-401) coatings were processed using two different thermal spray routes, i.e. HVOF and HVAF spraying. The influence of deposition route and processing conditions on the microstructure, porosity content, hardness and phase composition was examined. The as-deposited coatings were subjected to mild (5 N) and harsh (15 N) dry sliding wear test conditions by employing alumina ball as the counter surface material, and their wear performance was examined. Mild sliding wear test conditions (5 N) resulted in anomalous wear behavior, where the abrupt drop in CoF at several instances during the test was observed in all the investigated coatings. On the other hand, under harsh wear test conditions (15 N), such an abrupt dip in CoF was not observed. Detailed wear mechanisms of the coatings were revealed under different test conditions (5 N and 15 N). This work sheds light on processing, wear behavior and wear mechanisms of a sustainable and high-performance coating that fulfills non-toxic and sustainability goals in tandem for tribological applications. © 2022 The Authors
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| 4. |
- Musalek, Radek, et al.
(författare)
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Microstructures and properties of thermal barrier coatings deposited by hybrid water-stabilized plasma torch
- 2019
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Ingår i: Proceedings of the International Thermal Spray Conference. - : ASM International. - 9781510888005 ; , s. 738-745
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Konferensbidrag (refereegranskat)abstract
- Hybrid Water-Stabilized Plasma (WSP-H) torch provides high-enthalpy plasma which may be utilized for high-throughput and yet economical spraying of coatings from powders, suspensions, and solutions. It was previously demonstrated that microstructures and functional properties of the WSP-H coatings may be tailored to a wide extent for various new applications, namely those requiring high coating thickness and/or coating of large components. In this study, applicability of WSP-H technology for spraying of novel thermal barrier coatings (TBCs) is demonstrated. WSP-H technology was used for spraying of yttria-stabilized zirconia (YSZ) top-coats from powder, suspension and solution. Yttria content in the top-coat feedstock was 7-8 wt.%. NiCrAlY bond-coat was also sprayed by WSP-H and Hastelloy-X alloy was used as substrate material. Microstructure, phase composition, and endurance of the deposited coatings in thermal cycling fatigue (TCF) test were evaluated. Each thermal cycle consisted of rapid heating to 1100 °C, followed by one hour dwell and rapid cooling. All coatings showed excellent stability and TCF resistance withstanding more than 700 cycles surpassing in TCF test some of the currently commercially used TBCs. Lifetime of TBC with columnar top-coat deposited from suspension exceeded even more than 900 cycles. © 2019 ASM International. All rights reserved.
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| 5. |
- Musalek, Radek, et al.
(författare)
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Microstructures and Thermal Cycling Properties of Thermal Barrier Coatings Deposited by Hybrid Water-Stabilized Plasma Torch
- 2020
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 29:3, s. 444-461
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid water-stabilized plasma (WSP-H) torches provide high-enthalpy plasma which may be utilized for high-throughput and yet economical spraying of coatings from powders, suspensions, and solutions. It was previously demonstrated that microstructures and functional properties of the WSP-H coatings may be tailored to a wide extent for new applications, namely those requiring high coating thickness and/or coating of large components. In this study, applicability potential of WSP-H technology for spraying of novel thermal barrier coatings (TBCs) is demonstrated. WSP-H technology was used for spraying of yttria-stabilized zirconia (YSZ) top-coats from powder, suspension, and solution. Yttria content in the top-coat feedstock was 7-8 wt.%. In addition, gadolinium zirconate (Gd2Zr2O7-GZO) was sprayed from suspension for comparison. NiCrAlY bond-coat was also deposited by WSP-H, and Hastelloy-X alloy was used as substrate material. Microstructure, phase composition, and endurance of the deposited coatings in thermal cycling fatigue (TCF) test and during high-temperature short-term annealing were evaluated. All coatings showed excellent high-temperature stability and TCF resistance withstanding more than 650 cycles, surpassing some of the currently commercially used TBCs. Lifetime of the TBC with columnar top-coat deposited from YSZ suspension exceeded even more than 900 cycles.
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| 6. |
- Tesar, Tomas, et al.
(författare)
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Increasing α-phase content of alumina-chromia coatings deposited by suspension plasma spraying using hybrid and intermixed concepts
- 2019
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 371:S1, s. 298-311
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Tidskriftsartikel (refereegranskat)abstract
- 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
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