Research on Vacuum Diffusion Welding Process of Titanium Alloy Pipe and Stainless Steel Lined Pipe

The vacuum diffusion welding process was used to realize the connection of TC4 titanium alloy pipe and 15-5PH stainless steel lined pipe. The influence of welding temperature, holding time and intermediate layer on the welding interface structure, interface diffusion behavior and welding rate was studied. The results show that when the welding temperature is 900℃, the holding time is 4h, and the Ni intermediate layer is 20-30 μm, the welding between TC4 titanium alloy pipe and 15-5PH stainless steel lined pipe can be achieved, and the welding rate is the maximum. The interface product composition of the welded joint is TC4- (α+β) -NiTi₂-Ni_xTi_yP_z-Ni₃Ti-FeNi₃-γ- (15-5PH) from the titanium alloy to the stainless steel. The welding temperature and the intermediate layer are the most important factors affecting the diffusion connection. If the temperature is lower than 880℃or the intermediate layer is not used, reliable connection cannot be achieved. When the holding time is 4 h, with the welding temperature increasing from 890℃to 910℃, the welding rate and the diffusion layer thickness increase first and then decrease slightly. When the welding temperature is 900℃, with the holding time increasing from 2 h to 4 h, the welding rate and the diffusion layer thickness increase.