Hardening Effects of In-Situ Aging for a Laser Welded Maraging Steel

Abstract

Maraging steels are ultra-high strength alloys which have been successfully laser welded to obtain structural components. For most of the applications these steels are in an aged state to attain tensile strength up to 1.5 GPa, although welding induces local softening due to dissolution of precipitates. This paper aims to investigate the effect of in-situ aging of the maraging steel plates after laser welding to reduce the local softening. For a preheating at 40°C, just below the martensite finish line, the hardness of the Fusion Zone (FZ) attained between 440 and 490 HV and the Heat-Affected Zone (HAZ) attained a maximum of 570 HV compared to 300 HV of the Base Material (BM) for aging temperatures between 450°C and 520°C and periods between 10 and 30 min. The intercritical aging (570°C/1 h) also promoted an increase in local hardness of FZ 320 HV and HAZ 400 HV. Using an intercritical aging, the hardness situated between room temperature and quenched and aged coupons and was more homogeneous considering FZ, HAZ and BM. The microstructure of the intercritical aged welds is marked by duplex-ferrite and martensite micro-constituents