Influence of isothermal post-treatment on tribocorrosion behaviour of laser powder bed fusion-processed $β$-type Ti-Nb alloy

biocompatibility.Nonetheless, their cast and solution-treated forms suffer from limited mechanical strength. LPBFprocessedTi-Nb alloys hold significant potential for customized implants. Applying post-heat treatments,particularly isothermal age-hardening, can strengthen these alloys and improve their resistance to the biomechanicalloads encountered in service. However, load-bearing implants are prone to tribocorrosion due to therelative motion between implant components or between the implant and surrounding tissue in body fluids.This study investigates the mechanical, corrosion, and tribocorrosion properties of post-treated LPBF-producedβ-type Ti-42Nb alloys, and compares their performance with both as-built LPBF Ti-42Nb and conventional Ti-6Al-4V ELI. Results show that isothermal heat treatment is effective in increasing the mechanical propertiesby introducing ωiso precipitates for Ti-42Nb (LPBF-300 ◦C 30 h) and αiso’’ precipitates for Ti-42Nb (LPBF-450 ◦C30 h) to the single β-phase microstructure. Tribocorrosion behaviour was investigated under open circuit potential(OCP) and anodic potentiostatic polarization conditions (0.6 V vs. Ag|AgCl) in phosphate-buffered saline(PBS) using a reciprocating pin-on-disk tribometer. The formation of precipitates does not adversely affect thepassive film, indicating that its stability is maintained by the strong passivating nature of Ti-Nb alloys. However,the tribocorrosion resistance declines following isothermal heat treatment, likely due to the rapid detachment ofhard and brittle precipitates, leading to increased material loss. Nevertheless, controlling the distribution ofprecipitates in LPBF-fabricated Ti-42Nb alloys may enhance their performance for implant use.