Cavitation erosion behavior of laser gas nitrided Ti and Ti6Al4V alloy

A CW 2 kW neodymium-doped yttrium–aluminum–garnet (Nd-YAG) laser was used to carry out the gas nitriding process on commercial pure titanium and Ti6Al4V alloy. The microstructure, surface appearance, hardness depth profile and the cavitation erosion behavior of the nitrided samples in 3.5% NaCl solution were examined. The microstructure of the nitrided layer is mainly composed of TiN dendrites, of which the density gradually decreases towards the interface between the nitrided layer and the substrate. The cavitation erosion resistance of the nitrided samples was significantly improved as compared with the untreated samples. Increase in the surface hardness and the fine dendritic structure of the TiN layer contribute to the significantly enhanced cavitation erosion performance of Ti and Ti6Al4V alloy.