The Significantly Enhanced Mechanical and Tribological Performances of the Dual Plasma Nitrided and PVD Coated Ti6Al4V Alloy

In this work, plasma pre-nitriding technique has been employed to enhance the bearing capacity for the TiN coating deposited on Ti6Al4V alloy by magnetron sputtering. The composition, morphology and mechanical property of the as-prepared samples were studied by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), Vickers micro-hardness tester and nanoindentater. The tribological properties are investigated using a rotary tribometer under dry sliding and oil lubrication, and the mechanism was also discussed in details. The results show that the plasma nitriding treatment produced a nitrided layer with thickness of 85 μm on the surface of Ti6Al4V alloy, which significantly enhanced the mechanical properties. Therefore, the as-prepared TiN coated sample with plasma pre-nitriding treatment exhibit more excellent mechanical properties possessing the maximum hardness values (26 GPa) and exceptional load bearing capacity (74 N) compared to single TiN-coated Ti6Al4V. Moreover, the tribological properties of sample with plasma pre-nitriding treatment was also significantly improved, which was attributed to the synergistic effect of the superior bearing performance of nitriding layer and the high hardness of TiN coating. Additionally, wear mechanisms were discussed in terms of wear track morphology after sliding test.