PROGRESS IN X-RAY DIFFRACTION OF RESIDUAL MACRO-STRESS DETERMINATION RELATED TO SURFACE LAYER GRADIENTS AND ANISOTROPY

摘要

The well known sin~2 ψ method for macro-stress measurement elaborated for Bragg-Brentano geometry has some disadvantage e.g. penetration depth of X-ray beam varies during measurement. This is particularly important in the case of coatings or surface layers where residual stresses appear with large gradients. The new version of the sin~2 ψ method, named g-sin~2ψ (based on the grazing angle scattering geometry) was applied for determination of the macro-residual stresses in TiN coatings deposited on sintered WC and on sintered high speed steel. These types of samples present a wide range of residual stresses i.e. from large tensile to large compressive. Using the g-sin~2ψ method the stresses are determined for chosen near surface layers for which effective penetration depth remains almost constant during measurement. Anisotropic elastic constants were used for calculations. The measured results were compared with a model based on thermal shrinkage.