Effect of treatment time on Corrosion and Tribological behavior of Nitrocarburized coating by Cathodic Plasma Electrolytic Deposition

The cathodic plasma electrolytic deposition (CPED) was performed in alkaline electrolyte (glycerol + sodium nitrite) to form a nitrocarburized layer on AISI 1045 steel at constant voltage of 380 V. The results indicated that nitrocarburized layer was mainly comprised of epsilon-Fe2-3N, gamma'-Fe4N, Fe3C and Fe [Fe(CN)(6)](3) phases. As the treatment time was prolonged from 5 to 15 min, the surface porosity increased from 4.13 to 7.43%, while the thickness of layer was increased about 70% from 13 to 22 mu m. On the contrary, the corrosion test revealed that the coatings prepared at 10 min treatment time had the best corrosion resistance with a value of 27384 Omega.cm(2). Moreover, the mechanical behavior of coatings were also significantly increased by treatment time. The surface hardness increased 5 times, while the wear friction coefficient and wear rate of nitrocarburized layer were decreased to about and respectively compared to that of the substrate.