Effect of Nitriding Conditions on 304 Stainless-Steel Plasma Nitrided with Ni Screen

Abstract

This study investigates the effects of the treatment temperature and time on the S-DCPN (direct current plasma nitriding with screen) treatment using Ni screens. Austenitic stainless steel SUS304 is used as the substrate, and S-DCPN treatment is performed at treatment temperatures of 673, 723, and 773 K, treatment times of 4 and 16 h, gas pressure of 200 Pa, and treatment gas composition of 75% N₂ and 25% H₂. A Ni mesh is used as the Ni screen. The results of the S-DCPN treatment using a Ni screen on SUS304 after nitridation under each condition confirm that an expanded austenite (S phase) with supersaturated nitrogen solid solution is produced under all conditions, along with a nitrided layer. Ni deposits are formed on the sample surface under all conditions, as suggested by the X-ray diffraction patterns and optical microstructure investigations. The nitrided layer becomes thicker as the treatment temperature and time increase under all conditions. These results indicate that the nitridation efficiency improves upon using the Ni screen.