Plasma Nitriding and Its Effect on the Corrosion Resistance of Stainless Steel 1.4006

Abstract

: The plasma nitriding (PN) technology was applied on the martensitic stainless steel 1.4006. The influence of PN on the corrosion resistance of selected material was investigated. The chemical composition of selected steel was verified using the Q4 TASMAN device. The PN process was performed using two stage nitriding procedure. After plasma cleaning procedure at 515 °C for 45 min in a nitriding atmosphere ratio 20H2:2N2 (l/h) was the first stage nitriding procedure performed at 520°C for 16 hours in a nitriding atmosphere ratio 25H2:5N2 (l/h) and followed by the second stage of nitriding procedure performed at 525°C for 4 hours in a nitriding atmosphere ratio 28H2:4N2 (l/h). The microstructure and mechanical properties of the nitride layers were studied using OES spectrometry, optical microscopy, and hardness testing. The depths of plasma nitride layers were also estimated using a cross-sectional microhardness profiles measurement. The corrosion resistance testing of PN stainless steel 1.4006 samples were carried out in a 5 % neutral sodium chloride solution (NSS) in accordance with ISO 9227 standard in the VLM GmbH SAL 400-FL corrosion chamber and visually evaluated. Microhardness and surface hardness of experimental samples were significantly increased, but the corrosion resistance remarkably decreased.