RPB123;
I have come across this situation where we had to deposit Nitronic 60 weld metal over a 304L substrate for increased galling resistance. For your case, if you are joining Nitronic 60 to 316L stainless, I would use a Nitronic 60 bare wire (AWS 5.9 ER218) with the GTAW process.
Also, keep the interpass temperature below 350 deg F during welding. I would perform a liquid penetrant test of the weld just to make sure you have no problems.