I want to make small closed-type impellors for pumping cryogenic liquids (LOX, perhaps later LH2) under high stress, low weight conditions. This is for experimental purposes, at least at first. Suggestions for a production version are also welcome.
It's part of my ongoing effort to make turbopumps for bipropellant cryoliquid model rocket engines. :) I'll probably use mini-jet turbine parts for the turbines (if Wren ever answer my emails ...).
The impellor has complex interior surfaces, so I thought of making it up from computer generated plasma/laser (?) cut ~1 mm layers of 304 (?) stainless. I'd put removable tabs on the outside of each layer in order to get the registration right, and bulk braze them together to form a whole. Then heat-soak for a while, partly to distribute stresses and partly to allow the braze and the base metal to mingle.
Any suggestions for a brazing material?
I'd then like to coat all the interior surfaces in a lower melting braze, in order to smooth the interior surfaces - basically two-step brazing, except the second stage is just a covering/smoothing layer.
Again I'm looking for suggestions for a brazing material. I thought of using449 and 456, any comments? Any sources for 449 in small quantities?
Any other suggestions, comments?
The finished impellors will have to pump LOX at cryogenic temperatures.