Point load-induced fracture behavior in zirconia plasma spray coating

Heat-resistant coatings prepared by two different spraying methods: atmospheric pressure plasma spraying (APS) and high-pressure plasma spraying (HPPS), were tested using tungsten carbide indenters of different diameters, for the purpose of proposing the best suited method of indentation testing. It was found that with the APS method, the indentation load–depth curve gave the indentation depth and the residual depth smaller than and the yield stress greater than those with the HPPS. On the basis of fracture morphology in the cross-section, it has been conjectured that the APS coating has greater elastic modulus than the HPPS coating, and exhibits high strength exceeding debonding force between bond coat and top coat.