Determination of residual stresses in cathodic arc coatings by means of the parallel beam glancing X-ray diffraction technique

A method based on the parallel beam glancing X-ray diffraction geometry has been applied to the measurement of the residual stresses present in cathodic arc plasma (Al0.66Ti0.34)N coatings deposited on hardmetal substrates. This procedure avoids the problems associated to the strong overlapping between the diffraction peaks of the coating and the substrate. The method has been validated by comparison with the results obtained with sin2ψ technique on other combinations of coatings and substrates in which no important overlapping occurs (i.e. (Al0.66Ti0.34)N on steel and TiN either on steel or on hardmetal substrates). The elastic moduli of the different coatings, required for the calculation of the residual stresses, have been obtained from nanoindentation experiments.