Nd:YAG pulsed laser welding of dissimilar metals of titanium alloy to stainless steel

摘要

Pulsed laser welding of TC4 titanium (Ti) alloy to SUS301L stainless steel (SS) has been applied using pure Nb as an interlayer. Microstructures of the joints were analyzed by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Mechanical properties of the joints were evaluated by tensile tests. Based on avoidance of the formation of Ti-Fe intermetallics in the joint, two welding processes for the Ti alloy-Nb-SS joint were introduced. One process was one pass welding involving creation of a joint with one weld zone and a reaction layer separated by remaining unmelted Nb. The weld was formed while the laser was acted on the Ti alloy-Nb interface, and simultaneously, the reaction layer was formed based on interdiffusion and eutectic reaction of Nb and Fe at the Nb-SS interface. The mechanical performance of the joint was determined by the reaction layer at the Nb-SS interface with a tensile strength of 370 MPa. The other was two pass welding involving creation of a joint with two weld zones separated by remaining unmelted Nb, while the laser beam was focused on the Ti alloy-Nb interface and the Nb-SS interface, respectively. At this point, the mechanical performance of the joint was determined by the weld zone formed at the Nb-SS interface with a tensile strength of 171 MPa.