Influence of Ti/TiN bilayered and multilayered films on the axial fatigue performance of Ti46Al8Nb alloy

The effects of Ti/TiN bi- and multilayered films on the fatigue performance of the Ti46Al8Nb alloy were investigated. Ti/TiN films with a total thickness of 1 μm were deposited on the Ti46Al8Nb alloy substrate by the hollow cathode deposition method. The samples were examined with various analytical techniques including nanoindentation, scratch test, stripping layer substrate curvature test and scanning electron microscopy. The results show that multilayered Ti/TiN films can enhance the fatigue strength of the Ti46Al8Nb alloy, whereas bilayered films have no obvious effect. Compared with the bilayer, the multilayer exhibits higher hardness, higher residual compressive stress and higher adhesion strength to the substrate. It is also demonstrated that the multilayer is responsible for retarding fatigue crack growth. All the superior properties make the hard Ti/TiN multilayer to be an effective protection coating for the enhanced fatigue strength of the brittle substrate.