Effects of Thermochemical Surface Treatments on the Industrially Important Properties of X2CrNiMo 17-12-2 Austenitic Stainless Steel

Abstract

Austenitic stainless steels have low corrosion resistance in applications where strong acids and vapors attack the surface, typically in food and chemical industries. This drawback can be improved by surface treatments. Salt bath, gaseous or plasma-based surface treatments are a diffusion process for improving the hardness of the surface layer of stainless steels without significantly affecting their corrosion resistance. Low temperature nitriding and carburizing process can form a diffusion zone or/and compound phase. The corrosion-wear resistance of austenitic stainless steels can also improve with low temperature plasma nitriding and carburizing. The effect of these treatments on hardness and corrosion resistance was investigated in this research. Optical microscopy and Vickers hardness test were used for the characterization of the surface and potentiodynamic tests were performed to determine the corrosion rate. The results show that the hardness of the kolsterised sample is higher compared to the plasma nitride one. Beside this property, the corrosion rate is similar, but pitting corrosion was observed on the surface, due to the Cr₂N formation.