Formation of Oxynitride Layers on Titanium Alloys by Gas Diffusion Treatment

摘要

Titanium alloys were oxynitrided in controlled nitrogen-oxygen gas atmospheres between 650 degC and 950 degC for 5 h to 10 h with two different techniques of gas diffusion treatment. One technique was performed in an oxygen-containing (oxygen amount >= 0.4 percent) nitrogen environment. The other technique was performed in a deoxygenated (oxygen amount < 0.01 percent to 0.0005 percent) nitrogen environment with subsequent cooling in an oxygen-containing nitrogen environment (with an oxygen pressure of 1 Pa). The surface microhardness of oxynitrided samples increased due to the strengthening effect of titanium oxynitrides (TiN_xO_y). The maximum microhardness of the titanium oxynitrides was obtained with a near-equiatomic composition of nitrogen and oxygen in TiN_xO_y under optimal oxygen partial pressure and temperature-time conditions.