Back in the 60's we used to regularly have to re weld the combustion chambers on salamander salt heaters used in the oil and gas industry to melt the paraffin out of the crude those heaters were made out of inconel sheets. Not particularly difficult to weld as long as you used the correct filler rods and followed preheat and post heat procedures exactly. Other wise a small crack would become a large crack and radiate in several directions.
I've never welded any inconel castings but I suspect having to core weld up small imperfections would be a tedious process.