I think Ti alloy can be welded using TIG equipment without using an Argon filled enclosure. Bicycle frames are routinely welded up that way. ...........The interior of the tubes are purged of air and fed pressurized Argon through plugs in the tube ends.
desmo- Yes, some people do TIG weld titanium tubular structures like bicycle frames or exhaust headers using inert gas purge on the backside of the weld joint, and relying on the nozzle gas flow to shield the top side of the joint. But this is different situation than welding the joints of gearbox housing components (like those shown in Tony Matthews' illustration) where the backside of the weld joints cannot be sealed and purged. In these instances, manual TIG welding titanium usually requires a glove box.
Tony Matthews- Thanks for the reply.
As noted, DLS process can actually produce prototype titanium parts with fair metallurgical properties. However, wrought material weldments or HIP'd investment castings would give better properties. For a race team, the approach of using a weldment of machined parts is attractive because the work can all be done in-house, giving them control over schedule.
Investment cast titanium housing:
Lastly, here's a link to an extensive trade study done in 1975 by Sikorsky for a highly-loaded, fabricated main rotor gearbox housing on the CH-54 helicopter. Their conclusion was that the best option for weight, fatigue life and reliability was a welded truss structure made from Custom 455 stainless steel with bonded/riveted close-out panels. It's over 200 pages, but definitely worth a read.