Role of X-ray diffraction in evaluating component integrity

X-ray diffraction (XRD) is the most powerful tool for non destructive study of the fine structure of matter. A substance always produces a characteristic diffraction pattern, which is the bais for chemical analysis as that substance actually exists and not in terms of its chemical costituents. Both qualitative and quantitative phrase analysis are possible' as explained with referecce to determination of retained austenite. XRD is also used for measuring the residual stresses (macro as well as micro) based on the shifting and broadening of diffraction peaks respectively. The elastic strains are converted into stresses with the help of X-ray elastic constants. A methods for evaluating XEC is described. New developments based on these principles are also outlined.