Mechanisms of edge chipping in laser-assisted milling of silicon nitride ceramics

This paper investigates the mechanisms of edge chipping at elevated temperature in laser assisted milling (LAMill) of silicon nitride ceramics. Experimental results show that the elevated temperature can significantly reduce workpiece edge chipping through softening and toughening mechanisms. When the temperature is above the softening point and below the brittle/ductile transition temperature, the mechanism of elevated temperature on reducing edge chipping is through softening to decrease the cutting forces. When the temperature is above the brittle/ductile transition temperature, the edge toughness of silicon nitride ceramics is significantly increased. Both softening and toughening mechanisms take effect to reduce workpiece edge chipping. It is shown that temperature range between 1300 and 1400 °C has the most significant effect to reduce edge chipping in LAMill of silicon nitride ceramics.