Residual stress, mechanical and microstructure properties of multilayer Mo2N/CrN coating produced by R.F Magnetron discharge

We have investigated the effect of the period thickness of the multilayer Mo2N/CrN deposited on Si substrate produced by reactive magnetron sputtering. Mo2N presents a face centered cubic structure and CrN an orthorhombic one. The residual stress of the coatings was determined by the measurement of the substrate curvature. The microstructure of the multilayer was investigated from the X-ray diffraction and scanning electron microscopy (cross section images). The residual stresses resulting from the deposition of the different bi-layer thickness were measured and correlated to the structural properties of the coating as well as the nanoindentation analysis of the coating. The stresses are compressive and tensile for the individual Mo2N and CrN layer respectively. The result shows that an increase of the multilayer coatings Mo2N/CrN thicknesses induce an increase of the hardness and the elastic modulus, in the other hand the tensile stress increases. The shift of the XRD diffraction peak (1 1 1) of Mo2N at high angle which means the reduction of the residual stress is in good agreement with the residual stresses measurements.