The residual stress in as built Laser Powder Bed Fusion IN718 alloy as a consequence of the scanning strategy induced microstructure
The effect of two types of scanning strategies on the grain structure and build up of Residual Stress (RS) has been investigated in an as built IN718 alloy produced by Laser Powder Bed Fusion (LPBF) The RS state has been investigated by X ray diffraction techniques. The microstructural characterization was performed principally by Electron Backscatter Diffraction (EBSD) where the application of a post measurement refinement technique enables small misorientations 2deg) to be resolved. Kernel average misorientation (KAM) distributions indicate that preferably oriented columnar grains contain higher levels of misorientation, when compared to elongated grains with lower texture. The KAM distributions combined with X ray diffraction stress maps infer that the increased misorientation is induced via plastic deformation driven by the thermal stresses, acting to self relieve stress. The possibility of obtaining lower RS states in the build direction as a consequence of the influence of the microstructure should be considered when envisaging scanning strategies aimed at the mitigation of RS.
Scientific reports