Bonding titanium

Right, but even oil from your hands can embrittle a titanium weld. To get a strong join, the provess is very exacting.

But it isn't rocket science. We welded titanium in the Air Force, in fact I was certified to weld it as of about 1971. Chemically clean, don't contaminate the welding area, weld in an inert atmosphere.

For certification we welded in a Plexiglas box with attached gloves, purged before welding, but a mate who worked at the depot said that they welded it without using an inert box by using a heavier then normal gas flow and back purging as well. They were welding heating and pressurization ducts for the C-something and apparently there was considerable welding to be done.

As an aside, when certificating any color change at all after welding was reason for disqualification :-)

Yup.

You've just described "exacting."

Purged Plexiglass boxes with attached gloves; heavy argon flow; back-purging...

Jeez, John, do you weld steel trailers that way, too?

What you're describing is exactly what I was talking about.

It's tricky. The trickiness of making strong welds in titanium is the reason the Soviets made the MIG-25 Foxbat out of stainless steel.