Microstructure and Deformation Behavior of Additively Manufactured 17-4 Stainless Steel: Laser Powder Bed Fusion vs. Laser Powder Directed Energy Deposition

This study aims to compare the microstructure of 17-4 PH stainless steel (SS) manufactured via laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) in non-heat treated (NHT) and heat treated conditions. In addition, the room-temperature tensile behavior of heat-treated L-PBF and LP-DED 17-4 PH SS has been investigated and compared with that of the wrought counterpart with the same heat treatment conditions. The results show that the L-PBF specimens have a finer microstructure (ferrite + lath martensite) than the LP-DED ones (massive ferrite + Widmanstatten ferrite) in NHT condition. Electron backscatter diffraction analysis shows that the L-PBF and LP-DED specimens have twin-based substructure lath martensite after heat treatment. Despite the lower tensile strength of the LP-DED specimens compared with the L-PBF ones, the ductility of peak-aged LP-DED specimens was reduced due to the presence of the delta-ferrite phase having a significant plastic deformation incompatibility with the martensite.

Automated summary

This study compared the microstructure and tensile behavior of 17-4 PH stainless steel manufactured via laser powder bed fusion and laser powder directed energy deposition in heat treated and non-heat treated conditions. Despite differences in microstructure, the LP-DED specimens showed lower tensile strength and reduced ductility compared to the L-PBF ones due to the presence of the delta-ferrite phase.