KUSMIČ David Univerzita obrany

Spoluautoři HRUBÝ Vojtěch

Plasma nitriding technology, based on plasma assisted nitrogen diffusion into the steel surface, mostly used for improvement of wear resistance and fatigue strength is well known. Additional benefit of plasma nitriding is heat and corrosion resistance improvement. Corrosion is an undesirable process which is needed to be prevented or to be slowed. This study is focused on evaluation of corrosion resistance of plasma nitrided structural steels under several nitriding conditions. The experiments were performed on structural steels CSN 41 2050 (C45E), CSN 41 4220 (16MnCr5) and CSN 41 5230 (DIN 1.7361). Selected structural steels were manufactured for experimental specimens (size of 80x50x4 mm), heat-treated and plasma nitrided under following conditions: T = 500 (°C), process duration t = 10 and 20 (h), p = 280 (Pa), U = 510 (V) and variable gas mixture ratio of 3N2:1H2 (l/h) (to promoting the formation of Fe4N phase in the compound layer, so-called white layer) and 1N2:3H2 (l/h) (to promoting the formation of Fe2-3N phase in the white layer). Corrosion tests were carried out in the Liebisch GmbH & Co (S 400 M-TR) corrosion cell in the mist of neutral sodium chloride (NSS method), evaluated and documented in accordance to ISO 9227 standard and results compared to different plasma nitriding conditions. Under different plasma nitriding conditions were different nitride layer characteristics obtained. Nitride layers were by surface hardness (HV), metallographic testing and microhardness testing (HV0,05) classified. Using the microhardness testing were different values of microhardness and nitride layer depth detected, which was by the chemical composition of steels and different plasma nitriding conditions affected. Metallographic testing and additional concentration profiles measuring (using GDOES method) displayed different compound layers thickness, which tends to be a significant factor to corrosion resistance of plasma nitrided structural steels.