Influence of alloying by nitrogen on the strength and austenite stability of X18H10 steel

The strengthening and change in austenite stability when steel of X18H10 type alloyed by nitrogen are investigated, for applications where corrosion-resistant structural steel must operate satisfactorily at both high and cryogenic temperatures. Alloying by nitrogen may be regarded as a promising means of increasing the strength and stability of austenitic stainless steel. Preliminary cold or hot working increases the likelihood of martensite formation under load and consequently limits the working temperature range of the steel. High-strength nonmagnetic nitrogen steel based on X18AH10 steel with up to 0.22% N may be used for undeformable components at cryogenic temperatures. Without nitrogen, deformational martensite is always formed in such steel at temperatures below ?70°C. High strength, plasticity, and ductility may only be ensured in such steel by means of the TRIP effect or reduction in the grain size. Nitrogen effectively strengthens the solid solution in the high-temperature state. The use of combined high-temperature deformation and moderate-temperature deformation permits additional strengthening of the steel during thermomechanical treatment, including strain aging, which is effective where thermostable steel is required.