Wear mechanism of aggregated cBN grains during single-grain ultrasonic vibration-assisted grinding of γ-TiAl alloys

The wear mechanism of single aggregated cubic boron nitride (AcBN) grains during ultrasonic vibration-assisted grinding (UVAG) is investigated in this study. The experiments involve conventional grinding and ultrasonic vibration-assisted grinding on gamma titanium-aluminum intermetallic compounds, and the grain wear mechanism is comprehensively revealed by observing the radial wear height, normal force, average volume pile-up ratio, and morphology evolution of the grains under different conditions including maximum undeformed chip thicknesses, grinding speeds, and ultrasonic amplitudes. The experimental results demonstrate that the introduction of ultrasonic vibration induces periodic tangential vibrations in the workpiece, leading to intermittent dissociative behavior and effectively reducing the normal force and average volume pile-up ratio of individual AcBN grains during grinding. However, it also causes an increase in instantaneous maximum undeformed chip thickness and introduces periodic impact forces, thereby accelerating the radial wear height of the AcBN grains. Moreover, ultrasonic vibration can significantly diminish material adhesion on the surface of AcBN grains while promoting continuous micro-fracturing for enhanced self-sharpening ability. Nevertheless, excessive ultrasonic amplitude may result in macro-fracture of AcBN grains and expansion of bond cracks, leading to abrasive grain pull-out and partial loss of grinding capability.