Study On The Effects Of Hydrogen,Nitriding And Thermal Oxidation On The Properties Of Titanium Alloy

Titanium alloy is wieldy used in Aero space and military applications due to its low density,high specific strength and anti-corrosion properties.This paper studies the effects of Hydrogen on the microstructure and mechanical properties as well as the function of surface hardness of oxygen and nitrogen on titanium alloy.The reseach is significant to both the applications and manufacture procedures of titanium alloy. Investigation in this paper was concentrated on three main parts: (1) The influence of hydrogen on the microstructure,mechanical properties and tribology properties of the titanium alloy and behavior model was studied, in such a way that the manual hydrogen absorption was employed to acquire different contents on this titanium alloy. (2) The titanium alloy was nitrided under the atmospheres of NH3, NH3-O2 and pure N2, the microstructure, hardness gradient ,wear properties and nitrification mechanism of different atmospheres were studied . (3) The microstructure, hardness gradient ,wear properties and mechanism of thermal oxidation /vacuum diffusion of hardened layer of the titanium alloy was studied. In the first part, the microstructure, hardness gradient , ultimate tensile strength(σb),reduction of area(ψ)and impact strength(αk)of TC4 and TA2 was influenced by hydrogen. With the increase of the thermal cycling, ultimate tensile strength of the TC4 containing hydrogen increases, and the reduction of section area and impact strength decreases. In the second part, the nitriding layer was obtained under the atmospheres of NH3, NH3-O2 and pure N2,the results shows that using pure N2 may avoid the increasing of hydrogen in the nitrided layer. In the last part,the thickness and hardness of strengthened layer of the sample is about 180μm and Hv680 ,which is obtained by oxidizing at 850℃for 60min +24h vacuum diffusion at 850 ℃.This strengthened layer shows the best wear-resistance.