Hi Roy, I've never worked with nickel alloys before but I've welded plenty of dirty stainless which I hear they behave similar to.

At work they are talking about designing a Hastelloy X heat shield for the inside of a reactor. It will reach 2,000f and will have corrosive gases inside and be heat cycled repeatedly with a fast cool down. The design is a rectangular chute welded to the bottom of a flange. Inside the chute is where the combustion happens. 

We were thinking about breaking two pieces and welding them together to form the chute. I suggested we design the welded joints to be overlapping if possible and be welded on both sides of the lap joint. That's what I've done in the past on stainless tanks to handle heat cycling and remove stress from the joint.

I've read Inconel 625 should work for a filler but do you have any suggestions for filler, alloys to use, or design insight? Or just advice for welding nickel alloys?

Thanks