Preparation of Ca doping ZrO₂ coating on NiTi shape memory alloy by cathodic plasma electrolytic deposition and its structure, in-vitro bioactivity and biocompatibility analysis

The Ca doping ZrO₂ coatings were fabricated on NiTi alloys by cathodic plasma electrolytic deposition (CPED) technology. The CPED coatings exhibit a rough morphology filled with porous craters. The coating thickness is increased with the treatment time increasing. The X-ray diffraction (XRD) analysis shows that the coating is mainly composed of tetragonal phase ZrO₂ (t-ZrO₂). The X-ray photoelectron spectroscopy (XPS) indicates that the coating is composed by Zr, O, and Ca. The curves of potentiodynamic polarization suggest that the corrosion resistance of the NiTi alloy is significantly improved by the fabricated ZrO₂ coating. Ni ions release test shows that CPED coating could mitigate the Ni ions release effectively. The SBF soaking test shows that the ZrO₂ coatings exhibited excellent apatite-inducing ability, indicating the bioactivity of NiTi alloys is surely improved. The result of the osteoblast-like cells culture test shows that the adhesion, viability and proliferation of osteoblast-like cells on the ZrO₂ coatings are enhanced. It indicated that the obtained ZrO₂ coatings have good biocompatibility.