Alumina ceramic coating was prepared using plasma arc spraying, and the same ceramic coating with Fe-Cr-Al metallic intermediate
layer was also prepared using the same method. The
low-temperature thermal shock resistance of the resulting ceramic coatings at 600 ℃ was examined. The
thermal shock failure mechanism of the coatings was discussed. It was found that the low-temperature thermal shock failure of the titled ceramic coating was attributed to inter-layer and inner-layer cracks and their propagation, which led to peeling off of the ceramic coatings at weaker interfaces. Namely, the Al_ 2O_ 3 coating was weakly bonded to the substrate, thus the cracks were more liable to generate and propagate at the coating-substrate interface, which finally led to peeling off of the coating and hence thermal shock failure. Differing from the Al_ 2O_ 3 coating of mono-phase composition, the same ceramic coating with a Fe-Cr-Al metallic intermediate layer was characterized by poor bonding between the ceramic particulates, thus in this case the cracks preferentially emerged and propagated within the ceramic coating, which finally led to peeling off of the coating as well. In general, it was feasible to effectively increase the thermal shock resistance of the plasma arc sprayed ceramic coating by introducing a metallic intermediate layer, since the metallic intermediate layer was capable of relaxing the thermal stress in the coating and inhibiting the generation and propagation of the cracks.