Effect of heat treatment on microstructure and properties of VG10 and 3Cr13 dissimilar welded joints

Through laser swing welding of dissimilar steels, the microstructure and properties of welded joints of dissimilar steels under different heat treatment processes were investigated. In the test, the equilibrium phase diagrams of the base materials 3Cr13 and VG10 were calculated by JMATPro software. The microstructures of the different regions of the welded joints after the original and heat treatment were analyzed by XRD and SEM, and the changes of the microhardness were tested. The test results show that a martensite-like structure is generated at the base material on the 3Cr13 side of the original welded joint, and a non-convective mixing zone exists in the fusion zone on the VG10 side. At this location, a block-like, island-like structure is embedded in the base material. There were lamellar carbide formation on this structure. After heat treatment, the amount of carbides in the welded joints is reduced, but the primary carbides in the VG10 base metal are difficult to eliminate by heat treatment. In addition, the lamellar carbides in the VG10 side fusion zone are polymerized to form network carbides. The hardness of the base metal near the fusion line on both sides of the original welded joint is relatively large, and the hardness of the heat affected zone gradually decreases with increasing distance from the center of the weld. After heat treatment, the overall hardness of the welded joint has increased significantly. Among them, the hardness increase is greatest at the quenching temperature of 1050 °C, and VG10 can reach about 830 HV.