Laser-based powder bed fusion of non-weldable low-alloy steels
Journal article, 2021

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

Laser-based powder bed fusion

low-alloy steels

keyhole porosity

cold cracking

martensite tempering

lack of fusion porosity

intrinsic heat treatment

Author

William Hearn

Chalmers, Industrial and Materials Science, Materials and manufacture

Robert Steinlechner

Chalmers, Industrial and Materials Science, Materials and manufacture

Eduard Hryha

Chalmers, Industrial and Materials Science, Materials and manufacture

Powder Metallurgy

0032-5899 (ISSN)

Vol. In Press

Subject Categories

Manufacturing, Surface and Joining Technology

Other Materials Engineering

Metallurgy and Metallic Materials

DOI

10.1080/00325899.2021.1959695

More information

Latest update

8/20/2021