Experimental Characterization of Clad Microstructure and its Correlation with Residual Stresses

The repair of dies and molds used in the automobile industry by laser cladding (LC) is an important and emerging trend in additive manufacturing (AM) today. LC provides an alternative to the traditional deposition techniques which are ad-hoc and imprecise for powder metallurgical steels used in the repair of these components. The current study focuses on understanding the correlation between microstructure and the residual stress developed due to the deposition process. The microstructure was characterized using Electron Backscatter Diffraction (EBSD) analysis and the residual stress was measured using micro focus X-ray diffraction technique. The EBSD study revealed that the relative difference in martensite phase fraction resulted in local grain misorientations. A thermomechanical finite element (FE) model was also developed to predict the magnitude and nature of residual stresses in the component. The FE model calculated the stress field by considering only the thermal strain developed between the clad and substrate layers. The FE model was able to capture the nature of residual stresses in the clad and substrate where the thermomechanical effects dominate. The study revealed the importance of incorporating the effect of metallurgical transformation in FE model to accurately predict the residual stress variation in the substrate region.