engleski

Improvement of the corrosion resistance of carbon steel by nitrocarburizing process

Tribological (wear resistance) and chemical (corrosion resistance) properties of carbon steel can be improved by application of thermochemical processes such as nitrocarburization and oxidation. One of the most popular processes of nitrocarburizing in a salt bath is TENIFER® ; ; ; QPQ with post-oxidation. In the TENIFER® ; ; ; QPQ process steel samples are subjected to nitrocarburization in a salt bath at 580 °C, cooling down to the temperature of 350°C in a hydroxide bath, followed by cooling to the room temperature. After this procedure, samples can be polished and oxidized once more. The described process causes changes only in the shallow surface layer of the carbon steel sample in which formation of iron nitrides and oxides can be observed. The aim of this work is to study the influence of each of these process steps on the corrosion resistance of carbon steel. Investigations are performed by means of the electrochemical measurements (polarization resistance determination, Tafel extrapolation method, EIS) in a 5% sodium chloride solution. Surface roughness and microstructure analysis are also examined. The distribution of nitrogen, carbon and oxygen are measured with EDS.

nitrocarburizing; post-oxidation; carbon steel; corrosion resistance

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