Electron beam welding of pure titanium and nickel

This study presents the results of investigating the influence of welding parameters — beam power, beam offset relative to the joint, welding speed, and scanning frequency — on the formation of welded joints between commercially pure titanium grade VT1-0 and nickel grade NP2. It is shown that the weld metal structure consists of various types of intermetallic compounds, eutectics, and solid solutions based on nickel and titanium, with their ratio determined by the degree of penetration of the welded materials. The features of weld formation caused by the differences in the physical properties of the materials are described. The welding parameter ranges enabling high-quality weld formation have been identified. It is demonstrated that the presence in the weld metal of low-melting intermetallic Ti ₂ Ni and eutectic Ti ₂ Ni–Tiβ increases the tendency to crack formation and leads to brittle fracture of the welded joint. Almost all specimens fractured during tensile testing in zones containing a high proportion of Ti ₂ Ni and Ti ₂ Ni–Tiβ eutectic — either near the fusion lines or within the weld metal. Welded joints whose weld metal predominantly consisted of Ti ₂ Ni and Ti ₂ Ni–Tiβ eutectic failed before testing or within the elastic region of the tensile curve. A high content of titanium nickelide (NiTi) in the weld metal contributes to improving the strength of the welded joint. The maximum ultimate tensile strength of the welded joint reached 384 MPa, corresponding to 95% of the ultimate tensile strength of commercially pure titanium VT1-0.