Effect of Plasma Spraying Parameters on Anisotropic Feature of the Mechanical Property of Plasma Sprayed Al2O3 Coating

The effects of the plasma spraying parameters on the strength of an Al2O3 coating were investigated by changing the input electrical power to the plasma torch, the spray distance and the Al2O3 powder size as the spraying parameters. The anisotropic feature of the coating strength is also discussed. The strength of the Al2O3 coating in a direction perpendicular to a substrate plane was dominated by the layered structure of Al2O3 splats, and was affected by all the parameters. The strength of the coating in a direction parallel to the substrate plane was not affected by the input electrical power. The strength of the former was lower than that of the latter, in the coating containing many cracks. The anisotropy of the coating strength would be caused by the cracks propagating along the lines of the laminated layer.