Structural characterisation (AFM and XRD) and hardness of sputtered CrxNy coatings

Hard coatings for wear and oxidation/corrosion protection based on chromium nitride were deposited by means of a commercial rf magnetron sputtering unit with a mixture of nitrogen and argon from a target of the pure metal. This paper reports the influence of deposition parameters on coating morphology, crystallographic structure and hardness. The coating surfaces viewed by AFM show that the grain shape depends on the composition of the vapour phase, especially on the presence or absence of reactive gas. In addition, we paid a special attention to the first stages of growth. The crystalline phases Cr, Cr2N and CrN were identified by XRD analysis, as a function of the film nitrogen content. Finally, hardness measurements have been performed and compared to coating structure and composition.