Аңдатпа
The paper presents a study of the influence of plasma electrolytic carburizing (PEC) regimes on the structural, phase, microhardness, and tribological characteristics of structural steels. Plasma electrolytic carburizing was carried out in an aqueous solution containing 10% soda ash (Na₂CO₃) and 20% urea (CO(NH₂)₂), at a temperature of about 950°C and a voltage of 300V. Two cooling regimes were implemented after PEC for steel 20: natural cooling in the electrolyte and active nozzle cooling with electrolyte supply to the treatment zone, and for 30CrMnSiA steel only natural cooling in the electrolyte. The morphology of the structure and phase composition were studied using X-ray diffraction analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and optical microscopy. The results showed that the microstructure of steels after PEC morphologically has a zonal structure with a main martensitic phase with Fe₃C and Fe₇C₃ carbide inclusions. The microhardness profile was determined from the cross-section of the modified layer using a FISCHERSCOPE HM2000 device. Tribological tests were performed using the ball on disc method on a TRB3 machine under dry friction conditions at a normal load of 10 N and a sliding speed of 0.05 m/s. It was found that active cooling promotes the formation of a harder martensitic structure with maximum microhardness values of up to 430 HV for steel 20 and up to 720 HV for 30CrMnSiA steel, while their initial microhardness values were 170 HV and ~250 HV, respectively. It was also found that the coefficient of friction for these steels decreases by an average of 25–30% compared to the initial samples. The results confirm the effectiveness of PEC in forming hardened layers with increased microhardness and improved tribological parameters and demonstrate the potential of the method for use in the production of parts operating under high mechanical and frictional loads.