Influence of conventional and powder-metallurgical manufacturing on the cavitation erosion and corrosion of high interstitial CrMnCN austenitic stainless steels

High interstitial CrMnCN austenitic stainless steels combine superior mechanical properties with high resistance to corrosion. The first is caused by the strengthening effect of C and N and the low stacking fault energy leading to intense cold work hardening and e.g. increased resistance to fatigue, which implies a high resistance to cavitation erosion. Corrosion resistance is provided by the elements chromium and molybdenum. Usual manufacturing consists of casting, often followed by hot working. An alternative approach uses pre-alloyed, gas-atomized powders, which can be compacted either by hot isostatic pressing or supersolidus liquid phase sintering. The latter provides the possibility of adapting the nitrogen content via sintering atmosphere. This results in fully dense materials exhibiting comparable mechanical properties like the cast and hot worked alloys. In this study, high interstitial CrMnCN steels with different nitrogen contents were tested in an ultrasonic vibratory cavitation rig and analyzed by electrochemical polarization measurements using different electrolytes. The results indicate positive influences of increasing nitrogen content on both cavitation erosion and corrosion resistance. A comparison with cast and hot worked alloys is included.