CHARACTERISTICS OF NANOCRYSTALLINE COMPOUND LAYER OF ELECTROPLATED HARD CHROMIUM COATINGS AFTER PULSED PLASMA ELECTROLYTIC NITROCARBURIZING

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.