Influence of treatment conditions on the corrosion resistance of low temperature nitrided austenitic stainless steels

Low temperature nitriding is an effective method of surface modification of austenitic stainless steels, which allows to improve their surface hardness and tribological properties, but the treatment conditions depend on steel composition. In this research the influence of nitriding conditions on the microstructural, mechanical and corrosion resistance characteristics of the modified surface layers has been evaluated for a Ni-free steel, UNS S29225, and, for comparison, for AISI 316L and AISI 202 steels. The modified surface layers consist mainly of the so called S phase. Ni-free steel is more sensitive to nitride precipitation than AISI 316L, so that treatments should be carried out at temperatures lower than 400 degrees C. By choosing the appropriate nitriding temperature and duration it is possible to obtain a significant increase of corrosion resistance in a 5% NaCl solution, in comparison with the untreated alloy.

Automated summary

Low temperature nitriding is an effective method to modify the surface of stainless steels, improving their hardness and tribological properties. This research evaluates the influence of nitriding conditions on the microstructural, mechanical, and corrosion resistance characteristics of different steels.