Abstract
Zirconia–alumina composite coatings on the Type 304 stainless-steel substrate were performed by using the gas tunnel type plasma spraying apparatus without the metallic bond coat. The adhesive characteristics of the coating to substrate were investigated by using 3D analysis of the fracture surface. The alumina–zirconia composite coatings exhibited lamellar structure consisting alumina and zirconia layers, below 2 μm in thickness of a single lamella each other. Inside the lamellae, columnar grains were observed. Numerous microcracks occurred in the alumina splats or zirconia splats deposited during plasma spraying, and then fractured there by the tensile testing. The loose microstructure appeared near the interface between the coating and the stainless-steel substrate. The fracture morphology of the alumina–zirconia composite coating showed the round type pattern, which was related to the microstructure.
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