Surface oxygen diffusion hardening of TA2 pure titanium by pulsed Nd: YAG laser under different gas atmosphere

Titanium and its alloys are widely used in a variety of application in aerospace, automotive, chemical and biomedical industries. High affinity with oxygen limits their use at elevated temperatures. Exposure of titanium and its alloys to any oxygen containing atmosphere at elevated temperatures leads to formation of an oxide layer (OL) on the surface with an oxygen diffusion zone (ODZ) beneath it. TA2 pure titanium was surface treated by laser oxygen diffusion hardening for improving the surface hardness. The present study aims at characterization of the surface oxygen containing film formed in laser surface oxygen diffusion hardening process by mean of a scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS). The laser formed surface oxygen containing film is obtained by different gas atmospheres with oxygen, air, N-2, Ar+N-2 and O-2+Ar mixed gas. The hardening film on the TA2 surface has different colours, and has a certain thickness. The surface hardness can be as high as 1200Hv as compared with 310Hv for the as-received TA2 substrate. The findings show clearly that laser surface oxygen diffusion hardening process significantly improves the surface properties of the TA2 pure titanium.