Stereological investigation on structure/property relationships of plasma spray deposits

The mechanical properties of plasma sprayed alumina-13wt%titania deposits were studied employing indentation and four-point bend tests. Extensive quantitative microstructural information is required to better understand and explain the mechanical properties of thermal spray deposits. Stereology, which describes 3-D information using 2-D sections, has been applied to quantitatively investigate the microstructural features of thermal spray deposits. Stereology enables the generation of strict microstructural information which is not available directly from the analysis of metallographic cross-sections.; The relationship between mechanical properties and microstructure of plasma spray-formed alumina-13wt%titania (AT13) has been studied. Indentation and four-point bend tests were employed to determine elastic modulus, microhardness and strength of the deposit. The anisotropic behavior of these materials was also investigated. The anisotropy is attributed to the unique microstructure of thermal spray deposits; i.e., the spheroidal shape of pores and splats. The mechanical behavior of thermal spray deposits can be better understood by reliable and unbiased microstructural information. Stereological analysis has been applied to acquire quantitative microstructural indices of thermal spray deposits. The splat and void size-shape distributions were measured assuming the splats and voids were spheroidal in shape. The surface area of voids and splats were measured by using cycloid shape test lines. The degree of anisotropy of the surface area of splats and voids were also determined.; The five independent elastic constants were calculated from constitutive equations and the microstructural information (void aspect ratio and porosity) gained from stereological analysis. The calculated elastic constants were comparable to the experimentally determined values.