Laser-based powder bed fusion of non-weldable low-alloy steels

This study focuses on the processability of four low-alloy steels (AISI 4130, 4140, 4340 and 8620) via laser-based powder bed fusion (LB-PBF). In as-built condition, alloys consisted tempered martensite that was result an intrinsic heat treatment (IHT) during LB-PBF. terms defects, a distinct transition in porosity observed correlated to volumetric energy density (VED). At low VED, specimens contained lack porosity, while at high they keyhole porosity. Additionally, cold cracking 4140 produced low/intermediate VEDs. could be mitigated by increasing VED or laser power, as both enhance IHT. enhanced IHT lowered material hardness below specific thresholds (<500HV <460 4140), ductility allowing avoid cracking. From these findings, crack-free, high-density (>99.8%) steel were without requirement build plate preheating.