Study on the intrinsic correlation between thermo-mechanical properties and microstructural characteristics of plasma sprayed coatings

In this article, microhardness, bending strength and thermal diffusivity of plasma sprayed Al₂O₃ coating, as an example of typical thermal sprayed ceramic deposits, were comprehensively investigated in order to get a well understanding the intrinsic correlation between thermo-mechanical properties and microstructural characteristics of thermal sprayed ceramic coatings. It was revealed that as for thermal diffusivity, the porosity of coating is only first considerable (not determinative), but the splat interface density (d_SI) and pore interface density (d_PI) need more attractions due to their great contribution to the thermal resistance. Microhardness and bending strength value measured shows obvious anisotropy, and are closely related to the testing method, testing location among coating, microstructural defects and residual stress distribution. From the point of coating production enginering, these results not only contribute to better know the thermal spray theory, but also make on-site failure analysis and develop new coating products.