EB weld ss to tantalum

[NX687]

I dont have to actually melt the Ta do I

I can just sort of glue the SS around it to seal

Its for UH Vacuum and about 1000C operation

its a 19 dia x 0.5 mm wall Ta tube into a SS Flange ,

My main problem is cracking in about 20% of parts

 

[NX687]

I mean braze the SS to the Ta

 

[NX687]

I mean is it actually possible to do what Im doing

getting 316 to braze,,, weld,,, ,,seal,,,to Tantalum

for an Ultra high vacuum seal at approx 1000C operation

These parts are in service working , but I dont undersand if Im brazing SS to Ta or welding to it

No brazing matl is used at all

for contamination reasons ,

I just have a close fit

 

[MikeHalloran]

I think it's sort of welding, with an 80 pct yield.

Since you didn't provide a photo or a drawing, I'll hazard a guess that you're fillet welding what is a really thin wall tube to a relatively massive flange, and they're cooling at substantially different rates after welding.

In which case, I'd machine the flange from a thicker blank, and make the backside with a thinwall 316 'tube' projecting from it, so the weld can become more like a pipe butt weld, and the halves of the joint will cool at more nearly equal rates. Sort of like an ANSI weld neck flange, but with a much less massive neck.



Mike Halloran
Pembroke Pines, FL, USA

 

[NX687]

Yes , thanks

Similar sections , will try and get a picture

But I read that actually melting SS and Ta together makes a very weak matl

so you either use a filler type braze or if not


I sort of try and flow the molten SS over clean Ta and amazingly it glues tight , mostly, hope hope

its done in vacuum of course

60's EB Welder

The tube is a tightish fit in the flange

so on one I melted the Ta and SS together in a big weld and it looks like a good vac seal and heat seal ,


(1000C),

and seeing no mechanical strength is required


I feel it will work even though the mating of these materials as I say is a very poor alloy

 

[tbuelna]

There is a huge difference in the melting points of 316 cres and Ta. So it is unlikely that a fusion weld is being produced. And a brazed joint would imply that a tertiary material, with a melting point below that of either of the substrates, was used to bond the substrates without producing a phase change in them.

The most effective method for producing a joint between 316 cres and Ta would be to use some form of diffusion bonding process. A controlled application of temperature, pressure and vacuum.

 

[NX687]

Thanks
I will look up Diffusion welding

I can arrange temp, pressure and vacuum here