Louis,
Can you give some more detail?
I suspect you might be heating the work hotter and keeping it hot longer than you should, effectively dissolving alloying elements from the base and filler metals to their detriment. On that account it becomes necessary to know the composition of both, and what heating method you are using for the process.
It may be a problem to change the bronze, considering color variations among different alloys; presuming this is a decorative item it may be a concern, but excluding that, there are a variety of alternatives which begin to liquify and flow at a wide variety of temperature ranges... my impression is that there are fewer options for changing the chemistry of the stainless and the practical differences between them are, themselves, more limited.
Sooooo...... how thick is the brass (technically most often a bronze) layer, how are you heating it, how are you cooling it, how are you applying it, and how,where and when are the cracks developing? Any other detail I might have forgotten to mention you might think add, along with alloy designations, type of flux, etc. would also help.
Good luck with it.
Regards,
d
Hi Louis
It is possible that you are experiencing a failure mechanism called liquid metal embrittlement. It would be difficult to say for sure without having a lot more information, but you can try the following test to give you an idea where the problem lies:
1) Heat up you SS plate to a simmilar temperature as you do when brazing, but add nothing to the surface. (In your mind perform the same types of moves with the oxy-acetylene torch as when brazing.) If no cracking occurs here, then the problem is not the thermal stresses per se.
2) Add the flux to the surface while doing as above. If there is no cracking, then it is not due to the flux.
3) Add the brazing while doing as above. If it now cracks, then the problem lies with the addition of the brazing itself. In this case, almost surely liquid metal embrittlement.
Regards
Niekie Jooste
Hello Louis,
Have you considered having someone arc spray the bronze onto the S.S.? After spraying, the excess could be power brushed off or the part could be masked off with thermal tape prior to spraying. You could most likely hold part temp down to under 200°F using that process.
HTH,
Steve