Effects of boride coating on wear behaviour of biomedical grade Ti–45Nb alloy

Abstract This study investigates the tribological properties of as-received and borided Ti–45Nb alloys when paired with a WC-Co ball and examines the wear mechanisms that occur under dry sliding conditions. Pack boriding treatment applied to β type biomedical titanium alloy samples with improved structural and mechanical properties. The wear performance of both unborided and borided alloys, as well as the counterface and wear debris, were analysed using wear track measurements, weight loss techniques, and scanning electron microscopy. Unborided Ti–45Nb alloy underwent severe wear through multiple wear mechanisms, including tribo-chemical reactions, adhesion, and abrasive wear. Formation of a hard, bonded treatment layer on the Ti–45Nb alloy significantly enhanced its wear resistance up to certain load limits. In this case, mild polishing-type wear occurred, characterized by shallow scratches without weight loss. However, when the applied load exceeded the boriding layer’s load-carrying capacity, the surface layer was completely worn out by abrasive wear assisted delamination, and the alloy experienced severe wear resembling that of the unborided sample. Nevertheless, the volumetric wear rate is still 34 % lower than that of the unborided alloy. WC-Co ball was exposed to mild oxidative wear, particle detachment, abrasion, and micro-cracking wear mechanisms when rubbed against the harder boride layer.