钨和钢TIG熔钎焊接头的微观组织及力学性能

Microstructure and mechanical properties of TIG welding-brazed joint between tungsten and steel

采用Ni Cr Mo-3焊丝实现纯钨(W)和0Cr13Al钢的TIG熔钎焊接,利用OM、SEM、EDS、显微硬度计和电子万能试验机等手段研究接头的微观组织、成分分布、力学性能及断裂特征。结果表明:焊缝金属与钨母材形成的钎焊界面润湿性良好,钨母材表面溶解后的W原子扩散进入焊缝金属中,并在界面断续形成厚度不超过1μm的富W、Ni金属间化合物层;焊缝金属与钢母材形成的熔焊界面主要因Ni元素的扩散进入,在钢母材中沿熔合线形成宽5～10μm的马氏体层。焊缝金属大致可分为W原子固溶强化区、完全混合区和不完全混合区等三个显微硬度相差较大的区域。接头抗拉强度为167 MPa,断裂面主要位于距钨母材/焊缝金属结合面50～300μm的钨母材中,为典型的解理断裂形貌。

The dissimilar material joint between tungsten and 0Cr13Al steel was fabricated by TIG arc welding-brazing process with NiCrMo-3 wire as filling metal. The microstructures, composition distribution, fracture characteristics and properties of the joints were studied by OM, SEM, EDS, microhardness tester and electronic universal testing machine. The results show that NiCrMo-3 filler metal has a good wettability with tungsten. The W atoms from surface dissolution of tungsten diffuse into welding seam and the rich W, Ni intermetallic compound form on the interface of tungsten/welding seam which is discontinuous and the thickness is not more than 1 m. The martensite layer whose thickness is 5-10 m forms in steel along fusion line due to the diffusion of Ni element into steel. The welding seam can be roughly divided into W atom solid solution strengthening zone, complete mixing zone and incomplete mixing zone with great difference in microhardness. The tensile strength of joint is 167 MPa. Most of fracture surface is located in tungsten base metal and is 50 300 m from the tungsten matrix/weld seam interface. The fracture is typical cleavage fracture.