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Maraging steels have been used in many applications in aerospace due to their high specific mechanical strength. Nevertheless, welding is a challenge because of the local softening in the fusion and heat-affected zones. In order to increase the hardness of these zones, a post-welding heat treatment using a laser is proposed, i.e. the same laser responsible for the weld reheats the joint producing localized aging. Three millimeter thick 18 Ni 300 maraging steel coupons were bead-on-plate welded using 1800 W and speeds of 1.8, 2.4 and 3.0 m/min. Laser heat treatment was carried out using a 2 mm defocused beam, power of 130 W and scanning speed of 10 mm/min. Using this method, the hardness at the middle of the fusion zone increased from 270 to 340 HV, which is similar to the base material. According to the simulations, the laser post-welding heat treatment attained temperatures around 1000°C in the middle of the fusion zone with a period of 130 seconds above 500°C. The laser reheating induced the precipitation of an inter-dendritic intermetallic layer and tempered the intra-dendritic martensite. This method was proven useful for in-situ aging without need of further furnace treatments.
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