Microstructure and Properties of Intermittent Vacuum Nitrided Layer on TB8 Titanium Alloy Surface

TB8 titanium alloy was treated by intermittent vacuum nitriding at 800℃ for 6 h, and microstructure, hardness, wear and corrosion resistance of surface nitriding layer were studied. The results show that the surface inter mittent vacuum nitrided layer of TB8 titanium alloy was mainly composed of nitride layer with thickness of 60-80 μm and nitrogen diffusion zone with thickness of 110-130 μm, and the phases of surface layer were mainly composed of TiN, TiN_0.3, Ti₂AlN and α-Ti. The surface layer hardness reached 800-850 HV and decrease slowly from the surface layer to the center, and the center matrix hardness was 250-270 HV. Under the same condition, the wear loss weight of alloy treated by intermittent vacuum nitriding was only 1/12 of that of the untreated alloy, shallow and narrow wear traces were formed on the surface, and the wear resistance significantly increased. The corrosion rate of alloy treated by intermittent vacuum nitriding in mixture of HF and HNO₃ was about 1/153 of that of the untreated alloy, the obvious corrosion pit was not found on the surface, and the corrosion resistance greatly increased.