Wear Performance of a Novel Silicon Nitride Ceramic for Biomedical Applications

Abstract

Ceramic materials are sometimes used as bearing surfaces of joint implants due to their high wear resistance and biocompatibility. Silicon nitride (Si3N4) is one of the ceramics under investigation for such use, owing to its bacteriostatic properties and high wear resistance. Traditional Si3N4 is sintered using Al2O3 and Y2O3 as sintering aids. To improve the biocompatibility and bioactivity of Si3N4, new sintering aids (SrO, MgO, and SiO2) were used in this work. This substitution may however have substantial effects on the wear properties of the material. Hence, the aim of this study was to evaluate these effects. Multidirectional pin-on-disc wear tests against ultra-high molecular weight polyethylene pins were used to this end, running in fetal bovine serum solution at 37 °C for 2 million cycles. The surface roughness, phase composition, and surface morphology of the surfaces were investigated, together with the pH of the wear test lubricant and compared to a traditional Si3N4 composition. XRD and SEM results showed that the prepared ceramics were composed of α- and β-phase Si3N4. The surface roughness of the Si3N4 ceramic discs was in accordance with the biomedical standard, and the wear test results demonstrated that the new ceramics had a low wear factor and a comparable coefficient of friction to Si3N4 ceramics reported in previous work. However, the dissolution of the materials over time may be a concern for biotribological applications, such as long-term use or in other wear couples.