Oxide film thickness and composite mechanical properties of an ultrasonic-assisted ELID cast-iron-bonded grinding wheel

Ultrasonic-assisted electrolytic in-process dressing (ELID) grinding can be used in the high-efficiency and high-precision machining of difficult-to-process materials. This paper establishes a prediction model of oxide film thickness growth. We conducted ultrasonic-vibration-assisted experiments on an electrolytic cast-iron-bonded grinding wheel and carried out high-speed steel ball friction and wear tests. The mechanical properties and surface morphology of the oxide film were characterized by nanoindentation, SEM, and three-dimensional morphology. The relative error between the theoretical model and the measured data did not exceed 7%. With the increase in oxide film thickness, the oxide film on the surface of the cast-iron-bonded grinding wheel became looser, the film surface exhibited more defects, and the hardness and elastic modulus of the oxide film were far lower than those of the cast-iron-bonded grinding wheel substrate. The adhesion of the oxide film first increased and then decreased with the increase in film thickness; the complete peeling distance increased with the increase in film thickness. The thicker the oxide film was, the more likely it was to fracture and fall off, the larger the average coefficient of friction (COF), the higher the wear rate of the cast-iron-bonded grinding wheel, and the lower the cast-iron-bonded grinding wheel’s service life.