Anode plasma electrolytic boronitrocarburising of low-carbon steel

Multicomponent saturation of low-carbon steel with carbon, nitrogen, and boron was investigated under the anode plasma electrolytic treatment. Optical and scanning electron microscopes with an energy dispersive attachment were used to characterize the composition of the modified layer and its surface morphology. Surface roughness and microhardness were studied with a profilometer–profilograph and a microhardness tester; tribological properties were evaluated using a pin-on-disc tribometer at lubricated testing conditions. It has been established that the thickness of the oxide layer slowed down the diffusion of carbon, nitrogen, and boron as determined by the anode dissolution and high temperature oxidation, which are dependent on the processing temperature. Dissolution prevails over oxidation up to 850°C that results in the sample weight loss. At 900°C, the sample weight increases owing to oxidation which prevails over dissolution. The maximal boronitrocarburising layer thickness (0.11 mm) is observed at 850°C. The maximal microhardness of this layer is 880 HV after saturation at 850°C for 5 min. The friction coefficient and the wear rate of the samples treated at 850°C decrease by a factor of 2 in comparison with those of an untreated sample.