In this study, Ti-6Al-4V coatings were deposited by low-pressure plasma spraying (LPPS) using different powder sizes and spray currents. The coatings were also heat treated at different temperatures, after which their microstructure and properties were assessed. The results show that finer powders are more conducive to the preparation of dense coatings and that porosity is reduced by increasing plasma current. As for the effects of heat treating temperature, at 870 °C, the lamellar structure of the coating disappeared and was found to be fully equiaxed with a grain size of 5-10 µm at 1100 °C. Hardness also increased, becoming significantly higher than that of forged TC4 alloy following treatment at 1100 °C.

The equiaxed microstructure of 316L stainless steel coating was successfully deposited by low pressure plasma spraying (LPPS), which was different from the lamellar microstructure prepared by other thermal spraying technologies. In this article, the effect of substrate temperature during deposition process and post annealing treatment on the lamellar – equiaxed microstructural transition were investigated. The results indicated that the homogeneous equiaxed grains without lamellar boundaries coatings were observed when the deposition temperature was about 900 °C. Completely lamellar microstructural coatings were deposited at the substrate temperature of about 300 °C, and the lamellar microstructure can transform to equiaxed microstructure after annealing treatment. The hardness of equiaxed coating was lower than lamellar coating.