Microstructure and Wear Resistance of Low Pressure Nitrided Layer on TC4 Titanium Alloy Surface

The low pressure nitriding treatment at 820 ℃ for 10 h was conducted on the surface of TC4 titanium alloy to improve its surface hardness and wear resistance, and then the microstructure and wear resistance of the surface nitrided layer were studied by X-ray diffraction, optical microscope, scanning electron microscope, microhardness tester and wear testing machine. The results show that after nitriding treatment, the nitrided layer consisted of surface nitride layer and subsurface nitrogen diffusion layer was formed on the surface of TC4 titanium alloy. The nitrided layer was mainly composed of TiN, Ti2AlN and Ti3Al. The surface hardness of the layer was 800-900 HV, which was 3 times as much as that of the substrate, and the sectional hardness decreased with the increase of depth. Under the same condition, the wear mass loss of the nitrided sample was lower than that before nitriding treatment and increased more slowly with the increase of load, showing the great improvement of wear resistance.