Laser Welding Process of Titanium/Steel Dissimilar Metals Assisted by Laser Cladding V Transition Layer and Their Properties

Abstract:

Titanium/steel dissimilar metal structural components have great application prospects in multiple fields. In this work, the method of laser cladding vanadium (V) transition layer was adopted to assist the laser butt welding of Ti-4Al-2V titanium alloy and 06Cr18Ni11Ti stainless steel, and titanium/steel dissimilar metal joints with excellent microstructure and properties were obtained. Using high-purity vanadium (V) powder as the transition metal material, a certain thickness of V transition layer was prepared on the 4 mm-thick end face of Ti-4Al-2V titanium alloy by laser cladding equipment through a multi-layer and multi-pass cladding process, and the chemical composition, microstructure morphology and residual stress in the transition layer were analyzed. Subsequently, the V cladding sample was subjected to laser butt welding with 06Cr18Ni11Ti stainless steel to characterize the macroscopic morphology, microstructure, mechanical properties (tensile strength and impact toughness at high and room temperatures), fracture morphology and joint hardness of the titanium alloy+V transition layer+laser weld seam+stainless steel welded joint. The results show that during the laser cladding of V transition layer on titanium alloy, when the thickness of V layer reaches≥6.8 mm, the V content near the surface of the cladding metal is approximately 98wt%, and the Ti content decreases to 0.18wt%–0.22wt%. The average tensile strength at room temperature of the above-mentioned titanium/steel welded joints is 537.3 MPa, and the average tensile strength at high temperature (350 ℃) is 426.3 MPa. Moreover, the tensile specimen at room temperature fractures on the V cladding layer. The average impact toughness is 38.2 J/cm² (at the center of the weld seam), 102.6 J/cm² (in the heat affected zone, on the side adjacent to the V cladding layer), and 167.6 J/cm² (in the heat affected zone, on the side adjacent to the stainless steel). SEM analysis was conducted on the fracture surfaces of the tensile specimens. The fracture morphology shows that dimples account for the main part, and in some local areas, there are mixed fracture characteristics of dimples+cleavage or quasi-cleavage, indicating that both ductile and brittle fractures exist simultaneously, with ductile fracture being the main type.