TWI Industrial Member Report Summary 659/1998
L S Smith and P L Threadgill
Whilst solid state techniques are fairly well established for joining γ-TiAl, fusion welding processes may be preferable in some instances. Electron beam and laser welding processes have been applied to γ-TiAl alloys, but the primary disadvantage in the application of these processes is the requirement to apply very high preheats (>500°C) to avoid cracking. Whilst the tungsten inert gas (TIG) process has been used successfully with γ-Ti-Al, a high preheat is again required. Furthermore, the application of TIG welding, for anything other than limited repair purposes, is very limited due to the lack of a suitable consumable. A wire manufacturing route has been developed and the product applied successfully to TIG welding, but the cost of the consumable is prohibitive ($1000/lb).
Keyhole plasma welding is an alternative arc welding process which has been proven to be particularly suitable for welding in conventional titanium alloys. Single pass autogenous welds can be made in conventional titanium alloys up to approximately 18mm thick. If viable, keyhole plasma welding could offer a preferable alternative to TIG welding. Furthermore, if used to complete an autogenous root pass in thicker section components, then the amount of consumable required for subsequent TIG passes would be reduced markedly, bringing commensurate cost savings. The following programme of work was initiated to investigate the weldability of a γ-TiAl alloy using pulsed and continuous keyhole plasma welding.
- To determine the weldability of a γ-TiAl alloy using the keyhole plasma process.