Plasma-sprayed wollastonite 2M/ZrO2 composite coating

Wollastonite 2M/ZrO2 composite coatings in different proportions were deposited onto Ti–6Al–4V substrates using plasma spraying. The tensile adhesion test (TAT) specified by ASTM C 633-79 was used to measure the tensile bonding strength of the coating. The bioactivity of coatings was evaluated using a simulated body-fluid soaking test. The results obtained showed that the composite coatings have a lamellar structure with alternating wollastonite 2M and ZrO2 phases. The Vickers microhardness of composite coatings increases with increasing ZrO2 content. Carbonate-containing hydroxyapatite (CHA) was formed on the surface of the wollastonite 2M and wollastonite 2M/ZrO2 composite coatings soaked in simulated body fluid, but was not formed on the surface of the ZrO2 coatings after immersion. This indicates that wollastonite 2M and W7Z3 and W3Z7 coatings have very good bioactivity. In addition, a silica-rich layer appeared at the interface of CHA and wollastonite 2M and W7Z3 coatings, but is absent in the case of the W3Z7 coating. The ZrO2 in the composite coatings may decrease the dissolution rate of the coating in simulated body fluid compared to pure wollastonite 2M coatings.