遮熱コーティングの熱的・機械的特性に及ぼす高温曝露の影響

Abstract

Hot parts of gas turbine are subjected to a high-temperature gas environment. Thus, thermal barrier coatings (TBC) are coated on the surface of those components in order to protect the superalloy-based substrate from such aggressive environment. TBC is deposited by thermal spray technique, which is based on the deposition process of the continuous molten-particle impact onto the target. Thus, the mechanical properties of the deposits are affected by particle velocity, particle temperature and pre-heated substrate temperature as the spray condition. Previous study has examined about the influence of the spray condition on thermal and mechanical properties of the freestanding ceramic coating detached electrochemically from the TBC coated plate-shaped substrate. The results indicated that the particle velocity strongly affects the micro-hardness, elastic modulus and bending strength. In this study, the influence of high-temperature exposure condition on thermal and mechanical properties of the freestanding ceramic coating was examined as sequential report. As the results obtained by this measurement, it was found that the elastic modulus of the high-temperature exposed ceramic coating is lower than one of the as-sprayed coating. It was considered that this trend is caused by the increase in compliance of the overall ceramic coating by nucleation of microcrack along the splat boundary. It was also found as well as the results indicated in the previous report that Vickers hardness can characterize elastic modulus and bending strength of the freestanding ceramic coating with a correlation.