Plasma-sprayed zirconia bond coat as an intermediate layer for hydroxyapatite coating on titanium alloy substrate

This study aims to strengthen the bonding at HA coating/Ti-6Al-4V interface by adding an intermediate ZrO2 bond coat between them. The bonding strength of the HA/ZrO2 coating was evaluated with the separately prepared HA coating as control. The phase, microstructure and chemistry, and surface roughness of the plasma-sprayed two-layer HA/ZrO2 coating on Ti-6A1-4V substrate were investigated by X-ray diffractometry, scanning electron microscopy, and surfcorder, respectively. Experimental results indicate that the bonding strength increases from 28.6+/-3.22 MPa for HA coating to 36.2+/-3.02 MPa for HA/ZrO2 composite coating. Elemental analysis employed on the surface of ZrO2 bond coat, on which the HA top coat was first dissolved completely in HCl acid, reveals the sign of diffusion of calcium ions from HA to ZrO2 bond coat. In addition, rougher surface morphology provided by ZrO2 bond coat is also considered to aid in the bonding at HA/ZrO2 interface. Similar coating system done by other researchers is compared and discussed. (C) 2002 Kluwer Academic Publisher.