Effects of nitrogen flow rate on the microstructure and mechanical and tribological properties of TiAlN films prepared via reactive magnetron sputtering

Abstract

In this study, TiAlN ceramic films were fabricated via reactive magnetron sputtering on a Ti6Al4V titanium alloy substrate. The effects of N2 flow rates on the microstructure and mechanical and tribological properties of the films were systematically studied. With increasing N2 flow rate, the films underwent a morphological evolution from a fine columnar structure to a coarse structure with holes and microcracks. In addition, the preferred orientation of the films varied from TiAlN (220) to the (111) plane. However, a high N2 flow rate (≥20sccm) resulted in target poisoning and reduced the deposition rate, which resulted in defects such as cavities and holes on the surface. Moreover, with increasing N2 flow rate, the hardness and elastic modulus first increased and then reduced owing to grain refinement. The films deposited at a N2 flow rate of 16 sccm exhibited the smallest wear width and the lowest wear rate. As the N2 flow rate increased from 12 to 24 sccm, the wear mechanism of the films changed from abrasive and adhesion wear to abrasive wear caused by severe plastic deformation, which was directly related to the microstructural evolution and mechanical properties.