Synthesis and mechanical evaluation of nanocomposite coating layer of nc-TiN/a-Si3N4 on SKD 11 steel by sputtering

In this work, Ti–Si–N coating layer, one of promising nitride coatings to extend the life time of forming tools and other mechanical components, were deposited on SKD 11 steel substrate by a DC reactive magnetron sputtering technique. The coating layer was revealed nanocomposites, consisting of nano-sized TiN crystallites embedded in an amorphous matrix of Si3N4. Such microstructural characteristics of Ti–Si–N coating layer resulted in a significant improvement of hardness compared to common TiN coatings. Friction coefficient and wear rate of the coating layer significantly decreased with increase of relative humidity. The self-lubricating tribo-layers such as SiO2/Si(OH)2 played an important role in the wear behavior of the Ti–Si–N coating layer. It was found from our experimental results that the tribological behaviors of the Ti–Si–N coating layer were dependent on the factors affecting the tribochemical reaction, i.e., Si content and relative humidity rather than the hardness of coating layer.