激光熔覆V过渡层辅助钛/钢异种金属激光焊接工艺及性能研究

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

摘要:

钛/钢异种金属结构件在多个领域具有巨大的应用前景，本工作采用激光熔覆钒（V）过渡层的方法辅助钛合金Ti-4Al-2V与不锈钢06Cr18Ni11Ti激光组对焊接，获得了组织性能优异的钛/钢异种金属接头。以高纯钒（V）粉作为过渡金属材料，采用激光熔覆设备在4 mm厚度钛合金Ti-4Al-2V端面，以多层多道熔覆工艺制备一定厚度的V过渡层，并对过渡层中的化学成分、组织形貌及残余应力进行分析；随后将该V熔覆试样与06Cr18Ni11Ti不锈钢进行激光对接焊，对钛合金+V过渡层+激光焊缝+不锈钢焊接接头的宏观形貌、微观组织、力学性能（高温及室温抗拉强度、冲击韧性）、断口形貌及接头硬度等进行表征。结果表明：在钛合金上激光熔覆V过渡层，当V层厚度≥6.8 mm时熔覆金属近表面V含量约为98wt%，Ti含量降至0.18wt%~0.22wt%；上述钛/钢焊接接头的室温抗拉强度均值为537.3 MPa，高温抗拉强度（350 ℃）均值为 426.3 MPa，且室温拉伸试样断裂在V熔覆层上，冲击韧性均值分别为38.2 J/cm²（焊缝中心）、102.6 J/cm²（热影响区-临近V熔覆层一侧），167.6 J/cm²（热影响区-临近不锈钢一侧）；对拉伸试样断口进行SEM分析，断口形貌显示韧窝占主要部分，局部区域存在韧窝+解理或准解理的混合断裂特征，说明韧性与脆性断裂同时存在，以韧性断裂为主。

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.