Characteristics and mechanical properties of a (Ti, O, N)/Ti composite coating fabricated on NiTi shape memory alloy via PIIID

摘要

In this investigation, (Ti, O, N)/Ti composite coating was fabricated on a NiTi shape memory alloy (SMA) to improve its biocompatibility, bioactivity and wear resistance for its long-term medical applications, using the plasma immersion ion implantation and deposition (PIIID) technique. Scanning electron microscopic (SEM) examination of coating cross-sections showed that the (Ti, O, N)/Ti composite coating was uniform and compact. Energy dispersive X-ray (EDX) analysis not only indicated that the interface between the coating and NiTi SMA substrate was gradual rather than sharp, but it also showed the thickness of the composite coating to be ～ 1.0 μm. The EDX mapping of cross-sections of (Ti, O, N)/Ti composite coating revealed that Ni was not present on the surface of the coated samples. Nanoindentation tests were performed to evaluate mechanical properties of the composite coating. Pin-on-disc wear test results showed greatly improved wear resistance of (Ti, O, N)/Ti coated NiTi SMA.