| 1. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Effect of suspension characteristics on the performance of thermal barrier coatings deposited by suspension plasma spray
- 2020
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:1, s. 272-283
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the influence of suspension characteristics on microstructure and performance of suspensions plasma sprayed (SPS) thermal barrier coatings (TBCs). Five suspensions were produced using various suspension characteristics, namely, type of solvent and solid load content, and the resultant suspensions were utilized to deposit five different TBCs under identical processing conditions. The produced TBCs were evaluated for their performance i.e. thermal conductivity, thermal cyclic fatigue (TCF) and thermal shock (TS) lifetime. This experimental study revealed that the differences in the microstructure of SPS TBCs produced using varied suspensions resulted in a wide-ranging overall TBC performance. All TBCs exhibited thermal conductivity lower than 1 W/(m. K) except water-ethanol mixed suspension produced TBC. The TS lifetime was also affected to a large extent where 10 wt % solid loaded ethanol and 25 wt % solid loaded water suspensions produced TBCs exhibited the highest and the lowest lifetime, respectively. On the contrary, TCF lifetime was not as significantly affected as thermal conductivity and TS lifetime, and all ethanol suspensions showed marginally better TCF lifetime than water and ethanol-water mixed suspensions deposited TBCs. © 2020
|
|
| 2. |
- Ganvir, Ashish, 1991-
(författare)
-
Design of Suspension Plasma Sprayed Thermal Barrier Coatings
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal barrier coatings (TBCs) are widely used on gas turbine components to provide thermal insulation, which in combination with advanced cooling, can enable the gas turbine to operate at significantly higher temperatures even above the melting temperature of the metallic components. There is a permanent need,mainly due to environmental reasons, to increase the combustion temperature inturbines, hence new TBC solutions are needed. By using a liquid feedstock in thermal spraying, new types of TBCs can be produced. Suspension plasma/flame or solution precursor plasma spraying are examples of techniques that can be utilized for liquid feedstock thermal spraying. This approach of using suspension and solution feedstock, which is an alternative to the conventional solid powder feedstock spraying, is gaining increasing research interest since it has been shown to be capable of producing coatings withsuperior performance. The objective of this research work was to identify relationships between process parameters, coating microstructure, thermal conductivity and lifetime in suspension plasma sprayed TBCs. A further objective was to utilize these relationships to enable tailoring of the TBC microstructure for superior performance compared to state-of-the-art TBC used in industry today, i.e. solid feedstock plasma sprayed TBCs. Different spraying techniques, namely suspension high velocity oxy fuel, solution precursor plasma and suspension plasma spraying (with axial and radial feeding) were explored and compared to solid feedstock plasma spraying. A variety of microstructures, such as highly porous, vertically cracked and columnar, were produced and investigated. It was shown that there are strong relationships between microstructure, thermo-mechanical properties and performance of the coatings. Specifically, axial suspension plasma spraying wasshown as a very promising technique to produce various microstructures as wellas highly durable coatings. Based on the experimental results, a tailored columnar microstructure design for a superior TBC performance is also proposed.
|
|
| 3. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Failure analysis of thermally cycled columnar thermal barrier coatings produced by high-velocity-air fuel and axial-suspension-plasma spraying : A design perspective
- 2018
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 44:3, s. 3161-3172
-
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.
|
|
| 4. |
|
|
| 5. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Thermal conductivity in suspension sprayed thermal barrier coatings : Modelling and experiments
- 2016
-
Ingår i: Proceedings of the International Thermal Spray Conference. - : ASM International. ; , s. 368-374
-
Konferensbidrag (refereegranskat)abstract
- Axial Suspension Plasma spraying (ASPS) can generate microstructures with higher porosity and pores in the size range from submicron to nanometre. ASPS Thermal Barrier Coatings (TBCs) have already shown a great potential to produce low thermal conductivity coatings for gas turbine applications. It is important to understand the fundamental relationship between microstructural defects in the coating such as grain boundaries, porosity etc. and thermal conductivity. Object Oriented Finite element analysis (OOF) has been shown to be an effective tool for evaluating thermal conductivity for conventional TBCs as this method is capable of incorporating the inherent microstructure as an input to the model. The objective of this work was to analyse the thermal conductivity of ASPS TBCs using experimental techniques and also to evaluate a procedure where OOF can be used to predict and analyse the thermal conductivity for these coatings. Verification of the model was done using experimental thermal conductivity. Results showed that the varied scaled porosity has a significant influence on the thermal conductivity. Smaller grains, higher overall porosity content and lower columnar density resulted in lower thermal conductivity. It was shown that OOF could be a powerful tool to predict and rank thermal conductivity of ASPS TBCs.
|
|
| 6. |
- Ganvir, Ashish, et al.
(författare)
-
Thermal Conductivity in Suspension Sprayed Thermal Barrier Coatings : Modeling and Experiments
- 2017
-
Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 26:1-2, s. 71-82
-
Tidskriftsartikel (refereegranskat)abstract
- Axial suspension plasma spraying (ASPS) can generate microstructures with higher porosity and pores in the size range from submicron to nanometer. ASPS thermal barrier coatings (TBC) have already shown a great potential to produce low thermal conductivity coatings for gas turbine applications. It is important to understand the fundamental relationships between microstructural defects in ASPS coatings such as crystallite boundaries, porosity etc. and thermal conductivity. Object-oriented finite element (OOF) analysis has been shown as an effective tool for evaluating thermal conductivity of conventional TBCs as this method is capable of incorporating the inherent microstructure in the model. The objective of this work was to analyze the thermal conductivity of ASPS TBCs using experimental techniques and also to evaluate a procedure where OOF can be used to predict and analyze the thermal conductivity for these coatings. Verification of the model was done by comparing modeling results with the experimental thermal conductivity. The results showed that the varied scaled porosity has a significant influence on the thermal conductivity. Smaller crystallites and higher overall porosity content resulted in lower thermal conductivity. It was shown that OOF could be a powerful tool to predict and rank thermal conductivity of ASPS TBCs.
|
|
| 7. |
- Kumar, Nitish, 1995-, et al.
(författare)
-
Understanding the influence of microstructure on hot corrosion and erosion behavior of suspension plasma sprayed thermal barrier coatings
- 2021
-
Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 419
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal barrier coatings (TBCs) are bilayer systems comprising a 7–8 wt% yttria partially stabilized zirconia (YSZ) top coat deposited over a metallic bond coat. Suspension plasma spraying (SPS) is an advanced and attractive top coat processing technique due to its capability to yield a variety of microstructures, including the desired columnar microstructure for enhanced strain tolerance and durability. This work attempts to investigate the desirable microstructural features in an SPS processed TBCs to mitigate hot corrosion and minimize erosion related losses that are often responsible for coating degradation. SPS processed TBCs were deposited utilizing three different spray conditions to obtain distinct microstructural features (column density, interpass [IP] porosity bands, column width), porosity content, and mechanical properties. Apart from comprehensive characterization utilizing SEM, XRD and micro-indentation tests, the as-deposited TBCs were subjected to hot-corrosion tests in the presence of vanadium pentoxide and sodium sulfate as corrosive salts. Post-corrosion analysis revealed complete infiltration of the molten salts in all the investigated TBCs. However, the delamination cracks generated due to the infiltrated corrosive species were minimal in case of TBCs with higher fracture toughness. The differences in microstructure and mechanical properties also led to differences in erosion performance, with TBCs possessing minimal total porosity content and high fracture toughness best resisting erosion related damage. Post-erosion analysis revealed that the TBCs with higher fracture toughness and micro-hardness showed superior erosion resistance. Based on the erosion and corrosion results and subsequent post-mortem of failed specimens, plausible damage mechanisms are proposed. Findings from this work provide new insights on developing damage tolerant TBCs microstructures with enhanced durability when exposed to erosion and hot corrosion environments.
|
|
