Braised Joint Shrinkage

[dfly9891]

Can anyone add advice on the following topic?

I'm considering braising a titanium shroud to a titanium impeller using silver based braise compound. When choosing the best solder alloy for the job, what should I consider? CTE? Ductility? Interfacial Chemical Bonding Strength?

The diameter of the bond is about 1". The braised joint will be cooled to about 50K (-370 F). The braise weld that holds the shroud to the impeller will see some shear load during accel and decel (design speed of about 100,000 rpm). This is a constant velocity machine with low accel and decel values so the shear load should be the least of my worries.

I'm concerned about shrink rates of the joint and bonding strength. How do I keep the joint from cracking or separating?

Ideas?

 

[iainuts]

I've seen copper/copper and copper/stainless joints silver brazed. They do very well at cryogenic temperature. Don't know about titanium, but I'd think that as long as the bond is good at ambient, it will work well at cryogenic temp.