Microstructure and mechanical properties of a directionally solidified superalloy DZ411 plate sample repaired by laser melting deposition

In this study, directionally solidified superalloy DZ411 plate samples were repaired with IN738LC superalloy using the laser melting deposition technique (LMD), and the cause for the variable mechanical properties in different regions of the samples was then investigated by quantitatively analyzing the microstructure of the repaired samples. Since the & gamma;' phase precipitation strengthening effect of the LMD region was inferior to that of the casting substrate region, the LMD region had a lower yield strength than the casting substrate region. However, the ductility and ultimate tensile strength of the LMD region were both superior to those of the casting substrate region due to finer grains and finer and more uniform carbides in the LMD region. Although the ductility and yield strength of the sample containing the heterogeneous interface of the two alloys were com-parable to those of the casting substrate region sample, the tensile strength of heterogeneous sample was higher due to the generation of the geometrically necessary dislocation during heterogeneous interface deformation, which strengthened the heterogeneous sample. These results can serve as a reference for future LMD repair technology of directionally solidified superalloys.