Enhanced adhesion of plasma-sprayed commercially pure titanium porous coatings to polished Mg-PSZ ceramic substrates

The purpose of this study was to evaluate the suitability of a plasma sprayed titanium porous coating on polished magnesia-stabilized zirconia (Mg-PSZ) ceramic surfaces. We hypothesized that diffusion bonding was responsible for the adhesion of the coating to the ceramic substrate. Mg-PSZ tensile test coupons were vibratory polished (roughness Sa = 0.50 μm) or vibratory polished/lapped (Sa = 0.12 μm) before coating and testing. The exposed surfaces after tensile testing were examined by energy dispersive X-ray (EDX) analysis. Mg-PSZ shear test coupons were vibratory polished (Sa = 0.48 μm). As the surface roughness of the ceramic substrate decreased by a factor of 4.175, the coating tensile strength increased from 62.6 to 66.8 MPa, comparable to that of porous coated cobalt chromium (CoCr) and titanium (Ti-6Al-4V) coupons. EDX analyses found titanium everywhere on the ceramic surface after the titanium layer was pulled off with tensile testing, even on areas that appeared to be "clean" to the naked eye. This suggested that titanium oxide compounds were present at the interface, where the oxygen required could only result from diffusion bonding across the interface. Diffusion bonding may also explain the significantly higher amounts of zirconium on the coating surface that had been pulled off the smoother lapped ceramic coupons. The measured shear strength of porous-coated ceramic coupons was significantly higher than that of CoCr and Ti-6Al-4V coupons. The superior adherence of the titanium coating to Mg-PSZ suggests this process has great clinical potential in arthroplasty, especially for patients with metal sensitivity. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1925-1932, 2019.