溶射条件を考慮したセラミック遮熱コーティングの残留応力評価手法の提案

抄録

Thermal barrier coatings (TBCs) are applied to high-temperature components of land-based gas turbine (GT). In TBC deposited by plasma-spray process, spallation damage has been often observed in the component, because of subjecting to cyclic thermal stress due to start-steady-stop operation of GT. Thus, it is necessary to grasp the stress generated in the coating during service, in order to predict precisely life of TBC spallation. The coating stress is composed of residual stress formed by plasma-spray process and thermo-mechanical stress generated during the operation. The residual stress is especially known to take different value with dependence on plasma-spray condition (powder velocity and substrate temperature). This paper presents influence of the spray condition on the residual stress of TBC. Then, the residual stress evaluation method, which had been already proposed, is improved based on particle deposition modeling plasma-spray process. As obtained results, it was found that the residual stress measured by strain gage method increased compressively with a higher particle velocity. Influence of substrate temperature on the residual stress was very few. It was considered with the particle deposition model that the residual stress increased compressively with elastic modulus of TBC due to stronger splat-to-splat cohesion by high-speed impact of particles. The residual stress evaluation method was improved in consideration of the elastic modulus changing by particle velocity. The result estimated method agreed with one measured by the strain gage method.