Solution nitriding offers the possibility to enrich the case of near net shape parts, made of austenitic-ferritic duplex steel, with interstitially dissolved nitrogen. The case properties are given by the process parameters temperature, nitrogen pressure and time.

In the duplex grade X2CrNiMoN22-5-3, for example, a fully austenitic microstructure can be obtained by raising the nitrogen content above 0.60w/o. Rapid quenching is required to avoid M₂N precipitation. A pearlite-like austenite + M₂N ("nitrogenous pearlite") structure in the steel grade G-X3CrNiMoCuN26-6-3-3 is generated by adding 1.2w/o to 1.5w/o nitrogen and by applying slower cooling rates. Solution nitriding for 24 h leads to a case depth of up to 2.5mm.

The high nitrogen content results in a hardness increase and consequently in an increase of tensile strength of up to 60% compared to the solution annealed condition. This behaviour is related to the change of dislocation arrangement and to solid solution strengthening due to the interstitially dissolved nitrogen atoms. Beside the already known increase of corrosion resistance in high nitrogen steels the resistance against cavitation is strongly improved.

Due to these benefits solution nitrided cases are qualified for a wide range of applications. The precipitate-free case of the solution nitrided duplex steel X2CrNiMoN22-5-3 may be suitable for cavitation stressed parts in corrosive media, for example valves or impellers. The nitride-rich case of the steels X4CrNiMo27-5-2, X40CrNiMo27-5 and G-X3CrNiMoCuN26-6-3-3 seems to be more appropriate for parts stressed by erosion under less corrosive conditions.