X-ray residual stress analysis on multilayer systems: an approach for depth-resolved data evaluation

A data evaluation concept is proposed for the depth-resolved analysis of the residual stress distribution in polycrystalline multilayer systems (MLSs), which consist of alternating sequences of simultaneously diffracting layers of kind B and solely absorbing layers of kind A. This method can be applied to lattice strain data obtained in any diffraction mode used in X-ray stress analysis, such as the sin²ψ method realized in Ω, Ψ and `mixed-mode' geometry, or from measurements performed by means of the scattering vector method. The classical concept used for defining the X-ray information depth τ in the case of bulk materials is shown to lose its physical meaning for A–B–A–B... MLS structures. Starting from the idea of the diffraction power originating from an infinitesimal sublayer below the sample surface, an approach is introduced which weights the contribution of each layer B to the total diffraction signal by the attenuation due to the layer stack above. The formalism introduced in the article is verified by simulations carried out for different MLS geometries. Furthermore, it is applied to sin²ψ measurements performed on surface-blasted hard-coating systems consisting of Al₂O₃/TiCN layer stacks which were deposited by chemical vapour deposition on cemented carbide cutting tools.