Multi-objective optimization of tribocorrosion parameters and biocompatibility of selective laser melted CoCr alloy

This study investigated the biocompatibility and wear behaviour of cobalt chromium (CoCr) alloy fabricated using selective laser melting (SLM). A combination of Taguchi L₁₆ experimental design and multi-criteria decision making (MCDM) methods was employed to analyze the effects of wear parameters, such as load, speed, and time. Optimization was performed with respect to the weighting of criteria using a method based on the removal effect of criteria (MEREC) and multi-attribute border approximation area comparison (MABAC) for ranking the alternatives. The findings indicated that the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on MG-63 osteoblast-like cells showed excellent cell viability, confirming the biocompatibility of the 3D-printed CoCr alloy. Antibacterial tests indicated a cell viability of 83.4% on the alloy, leading to a stable Cr₂O₃ passive oxide layer, confirming its suitability for implants. Subsequently, the wear parameter was augmented, and an analysis of variance (ANOVA) was performed to determine the most influential parameter in the wear behaviour at a confidence interval of 95%. The optimal process parameters that enhanced the biological and tribological characteristics of the 3D-printed alloy were a load of 20 N, speed of 600 rpm, and time of 45 min (Trial 2). These resulted in a minimum wear rate of 1.16 × 10⁻⁶ mm³/Nm, friction force of 3 N, coefficient of friction (CoF) of 0.05, and average surface roughness of 1.88 µm. The improvements in the wear rate, friction force, CoF, and surface roughness were 12.2%, 13.04%, 12.5%, and 7.84%, respectively, when compared to the worst parameter (Trial 12). Also, the low current density (I) over the potential voltage (V) indicating corrosion resistance was in electrochemical corrosion testing. Wear analyses showed that ploughing tracks, grooves due to adhesive wear, and subsurface crack initiation due to fatigue were induced on the worn surface. This combined biological and tribological assessment provides significant insights for the design and optimization of implants.