Why Inconel 82?
According to my Inco alloys chart, Inconel 92 would be better.
For that matter 317L, 309L or 312L would likely work better.
I would recommend a light preheat of the parts to 300 - 500 degF.
You haven't stated how thick the pieces are, but Inconels don't like to
be cooled too fast and welding a heavy bar without preheat tends to
chill the weld quickly.
17-4 welds pretty easily as long as the welds can cool slowly and the
amperage is kept to a minimum.
Warming the parts prevents the welds from chill cracking.
I checked their site.
Special metals is a company that was formed by a merger of Inco Alloys
and a few other companies.
My older Inco chart shows 92 as better, but it seems they don't make 92
In fact they don't seem to make 82 either, even though it is still on
My favorite disimilar metals filler is Hastelloy W.
I too have had cracking problems on heavy sections if I didn't preheat.
Since your base metals are both stainless steels I would think a
stainless steel alloy might work better.
I still think 309, 312 or 317L would work better for your application,
but then a lot depends on intended use of the piece as far as heat and