Influence of Ultrasonic Rolling Extrusion Static Pressure on Corrosion Resistance of GCr15 Bearing Steel

The influence of static pressure during focused ultrasonic rolling extrusion on the corrosion resistance of GCr15 bearing steel was investigated. Quenched GCr15 bearing steel served as the subject of this study, wherein ultrasonic rolling extrusion was performed using a CNC lathe. Static pressure levels of 200 N, 400 N, and 500 N were applied during the experiments. Following the preparation of samples, which included grinding and cleaning, electrochemical assessments were conducted utilizing an electrochemical workstation. These assessments encompassed measurements of open-circuit potential, Tafel polarization, and electrochemical impedance spectroscopy, employing a three-electrode configuration. Additionally, the microstructural characteristics of the samples were examined using scanning electron microscopy, optical microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The findings indicate that an increase in static pressure results in a forward shift of the open-circuit potential and a reduction in corrosion susceptibility. Tafel analysis revealed an increase in linear polarization resistance, a decrease in corrosion current, and a positive shift in corrosion potential. The impedance spectroscopy results demonstrated that both the modulus of low-frequency impedance and charge transfer resistance increased with elevated static pressure. Microstructural analysis indicated that higher static pressure contributes to a smoother and more compact surface, with a reduction in defects. The primary corrosion products identified were iron oxides and hydroxides. In conclusion, the corrosion resistance of GCr15 bearing steel subjected to ultrasonic rolling extrusion is enhanced as static pressure increases.