Corrosion Resistance of Plasma Nitrided Austenitic Stainless Steel AISI 304 (X5CrNi18-10)

• Published in: ECS transactions 2020-11, Vol.99 (1), p.231-239
• Main Authors: Kusmič, David, Cech, Ondrej, Klakurková, Lenka
• Format: Article
• Language: English
• ISSN: 1938-5862; 1938-6737
• DOI: 10.1149/09901.0231ecst

In this paper, austenitic stainless steel AISI 304 (X5CrNi 18-10) has been subjected to low-temperature plasma nitriding (LTPN) at 400°C (673 K) in 24H2:8N2 (l/h), and in 8H2:24N2 (l/h) marked as LTPN-R, and to high-temperature plasma nitriding (HTPN) at 550°C (823 K) in 24H2:8N2 (l/h) working atmosphere, for 15h. The microstructure, microhardness, and phase evaluation of the nitrided steel were studied. The PN led to significant microhardness increase from 206 ± 3 HV0.05 to 842 ± 27 HV0.05 (LTPN), 821 ± 18 HV0.05 (LTPN-R), resp. to 1246 ± 27 HV0.05 (HTPN). The corrosion properties were evaluated using the anodic potentiodynamic polarization tests in neutral 2.5% NaCl deaerated solution. The corrosion rate CR (mm.a-1) increased only slightly for LTPN procedures. But using the HTPN increased 43-times to untreated steel, due to reduced passivation ability by chromium depletion by formed CrN. Additionally, the pitting was evaluated, and the pitting coefficient was calculated.