Effects of nitrogen content on microstructures and mechanical behavior of (TiTaCrMoNb)Nx films

The (TiTaCrMoNb)Nx films with nitrogen content were prepared on the surfaces of TC4 by magnetron sputtering. The effects of nitrogen content on the microstructures and mechanical properties of (TiTaCrMoNb)Nx films were investigated by x-ray diffractometer (XRD), scanning electron microscope (SEM), nanoindentation, high-resolution transmission electron microscope (HRTEM), electron probe microanalysis (EPMA), and laser confocal microscope. The results show that the deposition rates of the films decrease with the increase of the nitrogen flow. Besides, when N element is intoduced, the structures of the films change from the body-centered-cubic (BCC) to face-centered-cubic (FCC) phase composed of Me–N (metal nitride), which are preferentially oriented in the (111) crystal plane. Meanwhile, with increasing nitrogen flow, the hardness of the films shows a trend of first increasing and then decreasing. When the ratio of Ar and N2 flows is 25:25, the hardness and elastic modulus reaches the maximum value of 26.1 GPa and 311.8 GPa, respectively. The increase of hardness is mainly attributed to the formation of saturated Me–N and the solid solution strengthening. Meanwhile, the film behaves the best tribological performance, which presents a lowest friction coefficient and excellent wear resistance.