Laser metal deposition as repair technology for 316L stainless steel: Influence of feeding powder compositions on microstructure and mechanical properties

Laser metal deposition was used to repair grooves on 20 mm thickness 316L stainless steel plates using two different 316L stainless steel commercial powders - Fe-0.15C-11.8Cr-0.15Mn-0.2Ni-0.031P-0.56Si-0.05S (wt.%) powder and Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S (wt.%) powder. Good comprehensive performance of fine metallurgical bonding with were successfully achieved under optimized processing parameters. The microstructure and mechanical properties (micro-hardness, ultimate tensile strength, bending strength, low-temperature impact toughness) of the repaired specimens were investigated. Results indicated that chemical composition (different element contents) of the powders played an important role in determining the microstructure, phases and properties of the specimens. It was found that the microstructure of the specimens repaired with Fe-0.15C-11.8Cr-0.15Mn-0.2Ni-0.031P-0.56Si-0.05S (wt.%) powder was homogeneous and consisted of Cr-rich martensite while a number of cellular dendrite were presented in microstructure of specimens repaired with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S (wt.%) powder and the repaired specimens consisted of ferrite and austenite. Due to solid solution strengthening, the average hardness of the specimens repaired with former powder was higher than that of the specimens with later powder. However, in the aspect of mechanical properties, LMD with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S (wt.%) powder had better performance than the specimens repaired with another kind of powder. The relationship between the microstructure characteristics and mechanical performances of the repaired specimens was also discussed.