Study on the Microstructure and Properties of Nb/ZrO2/HA Composite Coatings by Plasma Spraying Process Parameters

In this study, niobium/zirconium dioxide/hydroxyapatite (Nb/ZrO2/HA) composite coating was deposited on ZK60 magnesium alloy by the plasma spraying technique. The effects of spraying power and the powder feeding rate on the surface morphology, corrosion resistance, surface hardness, and surface roughness were investigated in this study. Tests were conducted through the optimal parameter combination obtained during the optimization process. The Nb/ZrO2/HA coating consisted of α/β-TCP, TTCP, Nb2O5, HA, Nb, and t-ZrO2 phases. The results suggest that the Ca/P ratio of the coating approached the ideal calcium-to-phosphorus ratio characteristic of bone implant material surfaces. Under the parameters of 33 kw and 18 g/min, the coating exhibited a dense, flattened morphology with significantly reduced roughness of Ra = 2.128 μm. Compared to the pure HA coating, the surface hardness and corrosion resistance of the Nb/ZrO2/HA-coated sample increased by 28% and 56%, respectively. Furthermore, the mass loss rate in simulated body fluid (SBF) was considerably decreased by 33% compared to the HA coating. In vitro cytotoxicity assay reveals that the cell proliferation activity of the Nb/ZrO2/HA composite coating was higher than that of the HA/ZrO2 composite coating and the HA coating. Hence, the composite coating possessed favorable degradation controllability and biocompatibility.