Electron Beam Weld SS to Ta

[NX687]

I did post in Welding , but here might be better
Im trying to get 316 SS to take or braze or glue to Ta it seems to work in most cases

is there a matl I can use as a filler to enhance the bond


I have used tantalum in the moly to moly bond

and found that was good

 

[metengr]

Fusion welding will not work for this dissimilar material combination. Either diffusion bonding or friction welding are options.

 

[NX687]

Yes , vastly different melting temps

These work in Ultra high vacuum and 1000C

What Im doing is joining SS to tantalum pretty well , It must be a braze

In 20% of parts I get cracking and the SS, just a does not join to the Ta ,

I dont know why

Its not a metallurgy problem , just a how lucky I get trying to seal SS to Ta, not too cool and not too hot

 

[tbuelna]

These work in Ultra high vacuum and 1000C

So what you're saying is you need a brazed joint that can survive at temps above 1000degF? What is the brazing material you are using?

The reason you are getting cracks in your parts is likely due to a 2.5X CTE mismatch between the 316 cres and Ta. One thing you might consider doing to remedy the problem is optimizing the local section thicknesses of the mating parts at the joint so that the strains and stresses in both parts are more balanced both after brazing and during service.

Since you know the dimensions of the mating parts and the material properties of these parts and the brazing material, you should be able to calculate the relative strain in each part resulting from the joint cooling from the brazing temp to room temp. If your calculations show there is high enough stress produced in the 316 cres part from the CTE mismatch to cause failure, then you have a design problem. If not, then you likely have a metallurgical problem causing the cracking.

Good luck.

 

[NX687]

Tbuelna

Thanks
by CTE do you mean matl expansion difference

You know that SS is joined to Aluminium oxide for high vacuum and up to 250 Centigrade temperature application,
That type of strain relief method would work

In that case a braze matl is used , I wish to join the Ta to SS Directly for a 1000 Centigrade application , no braze matl is allowed