Temperature activated self-lubrication in CrN/Mo2N nanolayer coatings

CrN/Mo2N multilayers were deposited and TEM, SEM, EDS, XPS and TGA studies were carried out. TEM studies show crystalline layers with sharp interfaces. TGA studies indicate that the CrN protects the underlying Mo2N layers from oxidation. On varying the periodicity the hardness of the films are in the 20–30 GPa regime, within the rule of mixtures of its constituents. Friction tests at high temperature shows the films to have a temperature activated self lubrication mechanism. Similar friction tests in a near nitrogen atmosphere shows the same temperature activated lubrication mechanism operating with the friction being in a lower regime. MoO3 is isolated as the predominant oxides phase that evolves from the surface and at temperatures in excess of 400 °C acts as an in situ lubricant.