Laser gas nitriding modified on NiTi shape memory alloy

In order to improve the bioactivity of NiTi shape memory alloy (SMA). Laser gas nitrided layer was fabricated on the surface of NiTi SMA after irradiated by a continuous wave Nd-YAG laser in N2environment. It was studied that bone-like apatite formed on the surface of the acid and NaOH pretreated NiTi substrate and laser gas nitrided samples after immersion in simulated body fluid (SBF) at 37°C. Morphology and composition of the immersed samples' surface were characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and fourier transfer infrared ray (FTIR). It is believed that the composition of the deposition is similar to that of the bone-apatite. The results indicate that laser gas nitriding can effectively improve the ability of NiTi SMA to induce the formation of bone-like apatite in vitro environment. The formed layer has the Ca, P mol ratio of 1.57 very close to that of bone-apatite in SBF at 37°C.