Dave let me clarify. Titanium Nitride is a surface coating that needs to be stripped before welding. This is the gold coating that is on many taps, punches, and various steel working tools. Iron Nitride is what you are describing and yes that coating is not able to be stripped. It forms a case type of hardening that I have never seen greater than .008 thick (not to say it can't be deeper, but 1/16 seems impossible). This case usually ends up being 69-71 Rockwell C and is very wear resistant. We have welded parts with this coating without issue, but knowing the base metal is critical for pre/ post temp requirements. Depending on the size and area of the weld, it might need to be re-coated to maintain even wear when it goes back into service.