Microstructure and mechanical properties of 3D-GH3536/R-GH3128 butt joint welded by fiber laser welding with focus rotation

In this paper, the focus rotation has been adopted in the fiber laser butt welding of 4 mm thick Selective Laser Melting GH3536 and rolled solid solution GH3128. The weld morphology, microstructure, microhardness, joint strength and fracture morphologies were analyzed by using an optical microscope (OM), a scanning electron microscope (SEM), an electron back scattering diffraction (EBSD), a X-ray energy dispersive spectrometer (EDS), a microhardness tester and a tensile testing machine. The results showed that the focus rotation could effectively control the weld morphology, increase the fraction of high-angle grains in the welded joint, promote uniform distribution of Fe from 3D-GH3536 base material in the welded joint, realize grain refinement, and improve the microhardness of the welded joint. The tensile test results show that compared with the welded joint obtained in laser welding without focus rotation, the welded joint obtained by laser welding with focus rotation had higher strength. The strength of upper part of weld was increased by 6.12% to reach 98.8% of that of the 3D-GH3536 base material, while the strength of lower part of weld was increased by 8.30%. The welded joint obtained in laser welding with focus rotation has a fracture mode of ductile fracture.