A study on the surface quality of M50 bearing steel via low-temperature cold-air ultrasonic-assisted grinding

Abstract M50 bearing steel is extensively utilised in aerospace bearings due to its high hardness and excellent wear resistance. However, the high grinding forces and temperatures generated during conventional grinding (CG) can readily induce various forms of surface damage. The use of low-temperature cold air has been shown to suppress tool wear while improving the surface quality of the workpiece. Consequently, a novel machining method combining longitudinal-torsional ultrasonic-assisted grinding with low-temperature cold air processing was proposed to improve the grinding performance of M50 bearing steel. Grinding experiments were conducted to investigate the synergistic effects of the two technologies and verify the feasibility of the proposed method. A kinematic model of abrasive grain motion was established, and the surface topography of the grinding wheel was simulated. Furthermore, the surface topography of the workpiece was predicted. A low-temperature ultrasonic-assisted grinding test platform was developed for experimental investigations. The influence of process parameters on force-thermal characteristics and machining quality was analysed. The findings indicate that, in comparison with CG, cold-air ultrasonic-assisted grinding significantly enhances surface quality. Specifically, the measured surface roughness is reduced by up to 36%, tangential and normal forces are decreased by up to 43.7% and 46.8%, respectively, and the grinding temperature is reduced by up to 48.3%. The simulated surface topography agrees well with the experimental observations, thereby validating the model. The present study provides a theoretical foundation and process guidelines for the high-performance grinding of M50 bearing steel.