Influence of the nanostructuration of PVD hard TiN-based films on the durability of coated steel

High wear resistance of TiN/CrN is explained by an original propagation mode of the cracks due to a fluctuating residual stress field, evidenced by TEM and synchrotron measurements. Corrosion behaviour depends mainly on the nature of the outer layer. An external CrN layer, presenting a p-type semiconductive character, affords an enhanced protection. A beneficial role of the nanostratification, susceptible to strongly improve the density of films, was also evidenced. The high oxidation resistance of TiSiN is attributable to the network of refractory SiNx, which acts as a diffusion barrier for oxygen and insulates the highly reactive TiN nanograins from the aggressive atmosphere.