Abstract
Thin multilayer films, especially nitrides of transition metal, exhibit hardness enhancements that are significantly higher than those predicted by the rule of mixtures. In this study, TiN/CrN multilayers, consisting of alternating nanometer-scale TiN and CrN layers, were deposited by arc evaporation technique on M2 steel. Different period thicknesses Λ have been prepared: 10, 20, 40 and 60 nm. A recent study has shown that tribological properties enhancement of hard PVD nanostructured nitride coatings deposited on tool steel is optimum for a special period value of 40 nm with thicknesses of 24 and 16 nm for CrN and TiN layers, respectively. In order to get a better understanding of the mechanical behaviour of the coatings as a function of the modulation wavelength Λ, residual stresses in each nitride systems have been characterized using X-ray diffraction and the sin2ψ method at a synchrotron radiation facility. It is shown that the stresses are compressive and their magnitudes vary according to the type of nitride: CrN is less stressed than TiN. This might explain why the propagation of cracks into the whole multilayer coating is governed by the interfaces.
Published Version
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