Hydrogen Bake-out for Kovar

A. Hello Dale!

So why are you trying to get rid of hydrogen BEFORE plating? Sounds odd, since Kovar is a vacuum melted alloy that shouldn't have much if any H in it to begin with. Further, it also doesn't have a phase change (it's a low expansion glass sealing alloy, for Pete's sake) so you can heat it up to whatever temp you want, providing you protect it from carbon contamination. My CarTech brochure notes the permeability you get after annealing at 1000 °C and 1100 °C, so bake away, my friend!

Good luck!

A. Kovar is annealed in liquid hydrogen during the manufacturing process and it is difficult to remove all of the hydrogen from all of the grain boundaries, but you can try 300 or 350 °C bake (higher temp. may be okay, depending upon whether you plan further machining or not). If you can do it in nitrogen in a vacuum it is better. If you do the bake in standard air, you will oxidize the surface and it will be more difficult to plate or process. When you plate the Kovar you must do something to eliminate it from the gold plating because there will be a lot of hydrogen in that.
Hope this helps a little.