Substrate-constrained effect on the stiffening behavior of lamellar thermal barrier coatings |
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Authors: | Guang-Rong Li Juan Lei Guan-Jun Yang Cheng-Xin Li Chang-Jiu Li |
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Affiliation: | State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi''an Jiaotong University, Xi’an, Shaanxi Province 710049, PR China |
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Abstract: | Thermal exposure would compromises the compliance and thermal insulating performance of thermal barrier coatings (TBCs). However, most publications were based on free-standing coatings in which the stress resulting from substrate is essentially different from TBCs on superalloy substrate. In this paper, the constrained effect of substrate on the ceramic top-coat of plasma sprayed lamellar TBCs was investigated. Results showed that the structural changes evolve from micro-scale to macro-scale during thermal exposure. In a relatively shorter thermal exposure stage, the inter-splat pores became narrowed, whereas the intra-splat cracks became widened. Consequently, the healing kinetics of inter-splat pores was much faster than that of the intra-splat cracks. In a relatively longer thermal exposure stage, some macroscale cracks appeared in coating surface owing to the gradually stiffening coatings. As a result, the microscale intra-splat cracks near the macroscale cracks were healed rapidly. In brief, the substrate constraint induced structural changes were stage sensitive. |
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Keywords: | Substrate constraint Constrained healing Stiffening Thermal barrier coatings Structural evolution |
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