Study on Passivation Film Properties of GCr15 Bearing Steel by Electrochemical Machining

The passivation film was constructed on GCr15 bearing steel by electrochemical machining. The effects of different processing parameters on the thickness, microstructure, hydrophilic and hydrophobic characteristics of surface passivation film were studied. The results show that the processing voltage, electrolyte concentration and processing time are positively correlated with the thickness of the passivation film, and the maximum passivation film thickness of 29 μm can be achieved at the processing voltage of 9 V. The surface morphology of passivation film changes from granular to flake. Iron content decreases from 88.64% to 53.55%, chromium content decreases from 1.80% to 1.30%, oxygen content increases from1.16% to 18.96% and carbon from 7.81% to 25.97%. The chromium and iron content ratio increases from 2.20% to 2.43% and the stability performance improves. The water contact angle increases with the increase of processing voltage and electrolyte concentration. The water contact angle of the bearing steel surface changes from 78.4° to 130°, which can realize the modification of the surface from hydrophilic to hydrophobic, and the hydrophobic performance greatly improves.