Avoiding the high-temperature decomposition and softening of (Al1−xTix)N coatings by the formation of stable superhard nc-(Al1−xTix)N/a-Si3N4 nanocomposite

An approximately one monolayer thin amorphous Si3N4 tissue, that is formed during the deposition of the nc-(Al1−xTix)N/a-Si3N4 superhard nanocomposite coatings with their optimum structure and hardness, efficiently avoids the decomposition and softening of the fcc-(Al1−xTix) metastable solution to the titanium-rich fcc-(Ti1−δAlδ)N and the würtzite h-(AlN) up to a temperature of 1100 °C. In the absence of the Si3N4 skin, the decomposition and softening of (Al1−xTix)N occurs at about 800 to 900 °C.