Abstract: The nitrided layer of TC4 titanium alloy was prepared by using IPG high-power fiber laser in nitrogen atmosphere in this study. Effects of optical fiber laser power on surface morphology, microstructure and microhardness of the TC4 titanium alloy nitrided layer were investigated. Obtained results have demonstrated that the surface of the nitrided layer takes rough and smooth of two types. The microstructure of nitrided layer is dendritic, and that of HAZ is needle-like. When scanning speed takes 10 mm/s, the nitrogen flow rate is 10 L/min, the distance of the nozzle is 3 mm and the defocus reaches 0 mm, the penetration depth and width of the nitrided layer increase with the increase of laser power. In addition, the microhardness at the same depth from the surface of the nitrided layer increases with the increase of laser power.

Key words: TC4 alloy, laser power, microstructure and properties of nitriding layer, size of nitriding layer