Micro-resistance welding of precious metals

Hey all. Does anyone have any experience welding precious metals such as platinum alloys (platinum/nickel/tungsten) to other alloys, mostly a Ni/Cr
mix. Trying to get a sufficient weld of both .030 diameter platinum alloy spheres and .046 diameter by .100 long platinum alloy "cylinders" TO a flat .055 thk X .105 wide by "any length" Ni/Cr alloy. The weld is subject to extreme heat and presuure as well as chemical exposure. Right now using a Unitek/Myachi HF DC system with argon gas shielding. Still getting cracking at the weld interface under magnification. Basically, the weld is failing after an insufficeint amount of time and the welded alloy falls off the base metal. If anyone knows anything about this, even a little, I can provide some specifics on the weld parameters I'm using.
Thanks
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smooothakshun wrote:

I use an HF25 with 90 head, post your weld schedule.
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Thanks for responding. That's the same contoller I am using. It's a pretty basic upslope, weld, downslope schedule. No preheating or cooling or postheat. I'll post the schedule and force but I have to wait until I get back to work next week so I give you the "latest and greatest". The process is actually a "2-stage" resistance weld. The first station welds the alloy material to the base metal. The next station is simply a "coining" station that flattens the welded material out to specified size and the third station is a "re-weld" station that re-welds the material and attempts to re-flow the material because we have found that the coining (necessary) breaks the weld interface somewhat. I will post again as soon as I get the info. Both the welded and base alloys have a very high melting point which is necessary because of the extreme environment that the part goes in to. It has to withstand temps upward of 1000 F, pressures of 1000 psi, electrical arcing, and chemical deterioration. Thanks
I'll give you the exact make-up of the materials, too, by percentage of the elements.

Ni/Cr
alloy
flat
a
cracking
failing
base
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you guys are way beyond me ...I applaud you ~~~!

as
to
using
the
provide
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Thanks for the complement, butI don't know about all that way beyond us stuff. We all have our projects and industries we work in and this just happens to be what I am in to. I'm in the automotive industry and it's very competetive. From my descriptions, I'm not sure if you can figure out exactly what the automotive products are that I work with, but I think it may not be that hard if you really look at the descriptions I gave about the alloys and the sizes of the materials. I'll leave it at that. I could just really use some help with the "science" of welding what I am trying to weld. Working on this "micro" level can be a challenge. The product has to perform and hold up for a long duration under the absolute worst of conditions. Working with small parts greatly places limits on what amount of heat and pressure can be applied without destroying the parts being worked with. It's fun but not so fun at the same time. I guess it's a challenge. I just though all the welding "gurus" who congregate here might have some solid advice about what way to go. Next week I'll post the latest weld schedule and that should shed some more light on the subject. I'll give a better description of the process, too. Talking with anyone who has any experience with "micro resitance welding" and in particularly using Unitek/Myachi HF25 DC controllers would be greatly appreciated. Thanks for any help or suggestions that anyone provides.

such
a
subject
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