Nitriding

Enriching the surface layer of a material with nitrogen at low temperatures to produce an extremely hard and wear-resistant surface without quenching.

Nitrided steel has an extremely hard surface that quickly leads to cracks when welding. The hard edge layer must be completely removed before welding, otherwise the weld will crack. Welding onto the nitride layer is useless; it stays too hard and brittle. Once you've welded the steel, the nitride layer at the weld is gone anyway and must be rebuilt afterwards.

MetallurgieSchweißtechnik