A Study of X-Ray Residual Stress Gradient Analysis in Thin Layers with Strong Fibre Texture

Abstract

X-ray residual stress analysis (XSA) at thin polycrystalline layers with marked texture involves a series of difficulties, because the material becomes anisotropic on the macroscopic scale. In this case, the analysis of near surface residual stress gradients, which vary significantly within the penetration depth τ of the X-rays, is possible by means of the scattering vector method, where the lattice spacing depth profiles d φψ (hkl, τ) are measured after stepwise rotation of the sample around the scattering vector g φψ near the intensity poles of the texture. Individual stress profiles σ ij (τ) are then obtained directly from the d φψ (hkl, τ) distributions with the so-called stress factors F ij (hkl, φ, ψ, s mnop ) acting as proportionality constants, which reflect the macroscopic elastic anisotropy of the material. The paper gives a simple method for the evaluation of the F ij from the pole figures in the case of marked fibre textures. In the second part, the conception of the stress factors is applied to the analysis of the residual stress state in thin and highly (111) textured PVD coatings of Ti 1-x Cr x N.