An assessment of thermal shock resistance of AlCoCrFeNi/7YSZ thermal barrier coating

Abstract To investigate the thermal shock resistance of thermal barrier coating with AlCoCrFeNi high‐entropy alloy as the bond coating, this study prepared the AlCoCrFeNi bond coating on the 316L stainless steel substrate by vacuum plasma spray technique, and the 7YSZ ceramic coating was prepared by atmospheric plasma spray technique. The thermal shock resistance of the AlCoCrFeNi/7YSZ thermal barrier coating system was subsequently characterized by the water‐quenching test at 1000°C. The results showed that longitudinal and transverse cracks appeared inside the 7YSZ coating during the water‐quenching test. The longitudinal cracks mainly extended along the grain boundaries within the YSZ particles. In contrast, the transverse cracks primarily existed between the YSZ particles and the grain boundaries between the columnar grains and the equiaxed grains inside the YSZ particles. During the thermal shock process, the failure of the AlCoCrFeNi/7YSZ thermal barrier coating system was mainly concentrated inside the 7YSZ coating rather than at the interfaces. The thermally grown oxide layer of Al 2 O 3 was generated inside the thermal barrier coating system during the water‐quenching test. However, there was no significant effect on the failure process.