Nitriding hardening

Nitriding is a case hardening process where nitrogen diffuses into the surface of a steel component. You do this when you want a very hard, wear-resistant surface without losing core toughness. For welding, this means: if you have to weld a nitrided part, it's a tough nut. The nitride layer must be completely ground off beforehand, otherwise you'll get porosity and cracks in the weld. After welding, the layer is gone at that spot, so you either have to re-nitride the part or think of another solution.