Gas Nitriding
Anhydrous ammonia gas dissociates catalytically on component surfaces (490-530oC)
- nickel alloy retorts needed to prevent corrosion
- case depth 0.5mm after 45h at 515oC
White layer (~20mm) consisting of fcc g’ phase (Fe4N) and a hcp e phase with a higher nitrogen content formed at surface
Diffusion layer with alloy nitrides below