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| Abstract No.: |
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Scheduled at:
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Tuesday, May 10, 2016, Room 3C + 3D 3:00 PM
Ceramics Coating II
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| Title: |
Evolution of microstructure and properties of plasma sprayed YSZ constrained by substrate with different thermal expansion coefficient during thermal exposure
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| Authors: |
Guang-Rong Li / Xi'an Jiaotong University, P.R. China
Guan-Jun Yang*/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China
Cheng-Xin Li/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China
Chang-Jiu Li/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China
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| Abstract: |
During thermal exposure, sintering-induced thermally activated microstructural evolution of plasma sprayed thermal barrier coatings (TBCs) often reduces the coatings thermal insulation capability and compromises its strain tolerance. In this study, the YSZ was plasma sprayed on ceramic substrates with different thermal expansion coefficients (CTE) to investigate the CTE mismatch and rigid substrate constraint on sintering process and the associated structure/properties evolution. For the coating/substrate system without CTE mismatch, compared with free-standing coating, both the global and micro scale properties increasing showed similar retarding phenomenon, and the properties increasing rates was significantly anisotropic. The healing of inter-splat pores was more enhanced compared with intra-splat cracks, which resulted in the anisotropic shrinkage in coating. For the coating/substrate system with CTE mismatch, the structure and properties were more region-sensitive. The increasing rate for global properties was further retarded dramatically and the increasing scale was reduced notably during thermal exposure. While the micro-scale measurement results showed relatively larger discrepancy on properties at different regions. Some cracks connected at initial state under the CTE mismatch strain. Anisotropic evolution on cracking healing also occurred during thermal exposure. With the proceeding of thermal exposure, besides some wide intra-splat cracks remained opening under the constrained effect of substrate, some larger and wider cracks appeared on cross-section of coating due to sintering induced stiffening and shrinkage strain. The comprehensive effect of sintering and substrate constraint leads to the structure regionalization, namely the larger cracks remained opening and the neighboring regions became denser. This would benefit the further in-depth understanding of the thermal cycling failure mechanism of plasma sprayed TBCs.
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