Effect of N2 flow on low carbon TiAlNC coatings

TiAlNC coatings were prepared under various N2 flows by reactive dc magnetron sputtering. The composition, microstructure and hardness of TiAlNC coatings were investigated by energy dispersive spectroscopy, X-ray diffraction, scanning electron microscopy and micro Vicker tester. By increasing the N2 flow, the Al/Ti ratio and the nitrogen content of the coatings increased. It was found that hexagonal AlN phase precipitated under relatively high N2 flow (e.g. 8 sccm). The increase in the N2 flow also changed the preferred orientation of fcc Ti(Al)N(C) phase from random to [111], and then to [200]. The coating deposited at low N2 flow (e.g. 2 sccm) exhibited [111] preferred orientation with porous structure and relatively low hardness. However, when the N2 flow was relatively high (e.g. 8 sccm), the hcp AlN phase precipitation and N2-induced grain refinement resulted in a denser multiphase structure, which improved the hardness and toughness of the TiAlNC coating.