Tribological behaviour of biomedical Ti–Zr-based shape memory alloys

The tribological behaviour of Ti–30Zr, Ti–20Zr–10Nb and Ti–19Zr–10Nb–1Fe alloys was investigated using reciprocating friction and wear tests. X-ray diffraction (XRD) results indicate that Ti–30Zr, Ti–20Zr–10Nb and Ti–19Zr–10Nb–1Fe alloys are composed of hexagonal α′-martensite, orthorhombic α″-martensite and bcc β phases, respectively. Ti–30Zr alloy has the highest hardness of HV (273.1 ± 9.3), while Ti–20Zr–10Nb alloy exhibits the lowest hardness of HV (235.2 ± 20.4) among all the alloys. The tribological results indicate that Ti–30Zr alloy shows the best wear resistance among these alloys, corresponding to the minimum average friction coefficient of 0.052 and the lowest wear rate of 6.4 × 10⁻⁴ mm³·N⁻¹·m⁻¹. Ti–20Zr–10Nb alloy displays better wear resistance than Ti–19Zr–10Nb–1Fe alloy, because the iron oxide is easy to fall off and less Nb₂O₅ films form on the worn surface of the latter. Delamination and abrasive wear in association with adhesive wear are the main wear mechanism of these alloys.