Recently, new duplex surface treatments involving the use of pre-electroplating and pulsed plasma electrolytic nitrocarburizing (PPEN/C) have led to the possibility of using this material for applications usually typical for tool steels. In this work, we present results concerning the duplex treatment of preelectroplating of Cr and PPEN/C of AISI 1020 mild steel. The samples were electroplated in a plating bath. After electroplating, the samples were nitrocarburized. The effects of time and applied voltage of PPEN/C process were discussed. The samples were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and microhardness testing. Electroplated layers of up to 100 lm were obtained. The subsequent PPEN/C increased the surface hardness to 1200 HV 0.2 due to the formation of nitrides and carbides. Decreasing the size of nanocrystalline carbonitrides will lead to improvement of their wear resistance significantly.

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Electrolytic Plasma nitrocarburizing was carried out on the hard chromium coating deposited in SM45C mild carbon steel substrate by electroplating in two different times and voltages. The electroplated samples were connected cathodically to a high-current pulsed power supply and biased with a negative voltage of 400 V. The treatment times were 5 and 60 minutes. A 5-μm thick layer was formed on the surface of Cr coating with microhardness of about 950- 1200 HV0.1. The microstructure of the treated layers depends strongly on the treatment time length. The corrosion properties of the treated layers depend on microstructure and can be improved, especially if a thin and dense complex layer is produced at the surface.

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