Comprehensive analysis of pulsed plasma nitriding preconditions on the fatigue behavior of AISI 304 austenitic stainless steel

This study aims to draw an exact boundary for microstructural and mechanical behaviors in terms of pulsed plasma nitriding conditions. The pulsed plasma nitriding treatment was applied to AISI 304 austenitic stainless steel at different temperatures and durations. Results reveal that nitriding depth increased as process temperature and duration increase. The nitriding depth remarkably increased at 475 degrees C for 8 h and at 550 degrees C for 4 h. An austenite structure was transformed into a metastable nitrogen-oversaturated body-centered tetragonal expanded austenite (S-phase) during low-temperature plasma nitriding. The S-phase was converted to CrN precipitation at 475 degrees C for 8 h and at 550 degrees C for 4 h. Surface hardness and fatigue limit increased through plasma nitriding regardless of process conditions. The best surface hardness and fatigue limit were obtained at 550 degrees C for 4 h because of the occurrence of CrN precipitation.

Automated summary

The study indicates that pulsed plasma nitriding can significantly increase nitriding depth, transform austenite structure into S-phase, and eventually convert it to CrN precipitation. Surface hardness and fatigue limit are both improved, with the best results obtained at 550 degrees C for 4 hours.