Microstructural characteristics and mechanical properties of laser-welded Ta10W/GH3030 joints with beam offset

Abstract

Influences of the laser beam offset (LBO) on the microstructures as well as room-temperature and high-temperature mechanical properties of Ta10W/GH3030 dissimilar-material joints were investigated. In laser-welded Ta10W/GH3030 joints prepared under three conditions with LBOs of −0.2 mm (offset toward Ta10W), 0 mm, and + 0.2 mm (offset toward GH3030): the fusion zones (FZ) all contained expulsed substances Ni3Ta, NiTa, and Cr2Ta and their microhardness was certainly higher than the base metal (BM); a transition layer containing high contents of Ni3Ta, NiTa, and Cr2Ta phases was observed at the Ta10W/FZ interface. With the increase of the LBO, the contents of Ni3Ta, NiTa, and Cr2Ta in the FZ gradually declined, the average grain size in the FZ increased slightly, the microhardness of the FZ dropped rapidly, and the thickness of the transition layer at the Ta10W/FZ interface reduced obviously. Either in the room-temperature or high-temperature (750 °C) tensile tests, Ta10W/GH3030 joints were always fractured at the Ta10W/FZ interface, showing the typical brittle fracture mode, and the tensile strength of joints was enhanced with the increasing LBO. Under LBOs of −0.2, 0, and + 0.2 mm, the room-temperature tensile strengths of Ta10W/GH3030 dissimilar-material joints were 266.4, 308.6, and 341.2 MPa, while the high-temperature (750 °C) tensile strengths were 97.6, 191.5, and 202.7 MPa, respectively.