Titanium And Titanium Alloys Are Good Materials For Diffusion Welding

Titanium and titanium alloys are good materials for diffusion welding because their surface oxide films dissolve easily at diffusion temperatures. When liquid diffusion bonding is used, a layer of other metal must be placed at the interface between the titanium surfaces. Typically, this metal can form a low melting point eutectic with titanium. During the heating phase of brazing, the flow of liquid metal into the fit is irregular. At a later stage, the liquid layer diffuses into the base metal, allowing the weld to solidify completely before the end of the thermal cycle.

In recent years, the application of diffusion welding as a joining method for titanium and its alloys has attracted interest. Solid-state welding has the following limitations: the surface must be practically optically flat; diffusion must take place at a sufficiently low temperature in order not to affect the properties of the alloy, so diffusion is very slow. Liquid diffusion welding creates an unstable liquid film at the interface, which reduces the fit-up accuracy and also accelerates the diffusion process.

Since higher interfacial pressures and plastic deformation at high temperatures favor solid-state joining, it is sometimes possible to connect this sequence with a hot-working process that reduces the cross-sectional area of the material. Rolling diffusion joining is an example. In this process, titanium alloy parts are held in a titanium shell, which is evacuated and sealed into a mold. This type of welded joint is characterized by good strength, plasticity and corrosion resistance, but the difficulty is that the surface quality and process parameters are difficult to control and may affect the dimensional accuracy of the product. Another difficulty is that solid-state static diffusion joints must be made in argon or vacuum.
Titanium bar and titanium plate welding process:

(1) Titanium welding can be contact spot welding, seam welding, argon arc welding, plasma welding and electron beam welding and other technologies.

(2) It is generally accepted that commercially pure titanium and some low strength titanium alloys are weldable, but the higher strength titanium alloys are not ideal due to the decrease in plasticity after welding.

(3) Titanium cannot be welded to other metals by normal fusion welding methods because it will form metal compounds that form very brittle welds.