面内引張負荷を受けるサスペンションプラズマ溶射遮熱コーティングの内部応力分布

Thermal barrier coatings (TBCs) are essential for the turbine blades of high-efficiency gas turbine combined cycles. A typical TBC system consists of a metal bond coat (BC) with high-temperature corrosion resistance on a superalloy substrate and a ceramic top coat (TC) using the air plasma spraying (APS) process. Recently, the suspension plasma spraying (SPS) process enabled finer microstructural control than the APS one by using fine spray particles of sub-micron size with a solvent as a suspension. It has been reported that the TBC with a columnar structure sprayed by using the SPS method has superior thermal fatigue resistance. However, there is little information about internal stress distribution in the SPS-TBC. In this study, the internal stress distribution of the SPS-TBC with a columnar structure subjected to tensile loading was evaluated by the high-energy synchrotron X-ray and the low-energy X-ray diffraction analysis. Experimental results revealed that the internal stress in the SPS-TBC was lower than the conventional APS-TBC due to the stress relaxation mechanism of the SPS-TBC' s columnar structure. The SPS-TBC exhibited a periodic residual stress reduction in the out-of-plane direction. The finite elemental analysis was also conducted using the column structure models. Based on the comparison between the experimental and analysis results, the effect of microstructure on the internal stress distribution of the SPS-TBC was discussed.