X-ray diffraction methods for the evaluation of residual stresses in the surface layers with gradient structure

We propose an X-ray diffraction method aimed at measuring residual stresses in the surface layers characterized by variable chemical compositions over the depth of the layer. The method is based on measuring the interplane distances for different diffraction reflexes with separation of the contributions of elastic stresses and the composition of a solid Solution to these distances on the basis of specific features of the elastic anisotropy of the crystal lattices of metals with Cubic and hexagonal structures. The efficiency of the proposed procedure is demonstrated by analyzing, as an example, EI961 and 12Kh18N10T steek, PT7M titanium alloy after ionic nitriding, and EP975ID nickel superalloy treated by electroerosion cutting.