Surface zone analysis
Surface zone analysis
Surface zone analysis by X-ray diffraction
Residual stresses (RS) are amongst the material characteristics which influence the operating behavior of components and tools. Residual stresses include stresses which are active in a component without the effect of external forces, and therefore without loading. They arise and chan-ge due to thermal and mechanical impacts, amongst other reasons, from heat treatment, particular processing procedures (e.g. grinding, milling, shot peening, coating of component surfaces), or from loading in operation.
Due to the measurement of the lattice strains the X-ray microstructure analysis offers the possibility to quantify the residual stress state of the three dimensional space lattice of a crystalline material. Tri-axial RS-states can be evaluated as well as phase, macro and micro stresses in case of multiphase materials.
A further area of application is the phase analysis, which detects the existing crystalline material phases from the position of the diffraction lines and specifies their volume content from the intensity of the lines. A well known application of the method is the determination of the retained austenite content for the evaluation of the material states after heat treatment or plastic deformation.
Manipulations of the micro structure due to mechanical and thermal overrides can change the texture (orientation of the crystals), which can be illustrated with intensity pole figures.
Benefits of the surface zone analysis
Today high standards are asked for the useful properties of products. Therefore it is important to examine influences on the component quality, when introducing new manufacturing processes, tools and cooling strategies. The workpiece surface states of the functional areas of both operating partners are very important at the matter, since they are mostly exposed to special loads, like abrasive or chemical wear, Hertzian pressure and relative move. The causes of component failure, rudiments for improvement of manufacturing processes and future strategies for product developments can be derived from exact knowledge of the residual stresses and the contents of the material phases in connection with the classical analysis methods measurement of hardness and surface roughness, metallography as well as light and scanning electron microscopy.