1. Physico-Mechanical Institute of National Academy of Sciences, Lviv, 79601, Ukraine 2. School of Advanced Materials Science and Engineering, Sungkyunkwan University, 300, Cheoncheon-dong, Jangan-gu, Suwon-si, Gyeonggi, 440-746, Korea
Abstract:
Titanium alloys were oxynitrided in controlled nitrogen-oxygen gas atmospheres between 650 °C and 950 °C 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 %) nitrogen environment. The other technique was performed in a deoxygenated (oxygen amount < 0.01 % to 0.0005 %) 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 (TiNxOy). The maximum microhardness of the titanium oxynitrides was obtained with a near-equiatomic composition of nitrogen and oxygen in TiNxOy under optimal oxygen partial pressure and temperature-time conditions.