A tribological investigation of SLM fabricated TC4 titanium alloy with carburization pre-treatment

The tribological properties of SLM fabricated TC4 discs (before and after carburization) sliding against ZrO₂ ball at different loads (0.98–4.94 N) under bovine serum lubricated conditions were investigated by using a Ball-On-Disc (BOD) tribo-meter. In comparison, the friction and wear behaviors of the forging fabricated TC4 disc against a ZrO₂ ball were performed under the same lubricated condition, and the results represented the similar trends with the SLM fabricated TC4 (SLM -TC4). Meanwhile, the friction coefficients of SLM-TC4 and SLM-C-TC4 disc (SLM fabricated TC4 after carburization) against ZrO₂ ball both decreased with the increase of the load. Combined with the worn surface analysis and theoretical analysis, it can be concluded that the friction force of the sliding pairs mainly originated from the resistance of deformation and shear stress, and the friction coefficients are linearly correlated to negative one-third power of the normal load. Furthermore, a hard TiC layer was observed on the surface of SLM-C-TC4 disc, which may provide a certain anti-wear capacity between the sliding pairs because of its effective resistance to deformation and shear stress. Therefore, the SLM-C-TC4/ZrO₂ bearing couple showed significantly lower wear than that of the SLM-TC4/ZrO₂ bearing couple and forged TC4/ZrO₂ sliding pair. So, SLM-C-TC4 may be more suitable for joint prosthesis design.