Prevention of Depth-of-Cut Notch Wear in CBN Tool Edge by Controlling the Built-up Edge

During the cutting of Inconel 718 with a Cubic Boron Nitride (CBN) tool under roughmachining conditions, notch wear is prominently formed at the depth-ofcut line. In this study, close-up observations around the tool edge by a high-speed video camera were conducted to investigate the cause of notch wear. The results suggest that notch wear is caused by unstable extrusion of the Built-Up Edge (BUE) that forms under the chamfered edge as well as by secondary chip formation due to the side flow at the depth-of-cut line. The BUE extrusion behavior depends on the tool geometry, such as the chamfer angle, the chamfer width and the rake angle. The secondary chip easily forms if the curled BUE is unstably extruded. However, the stable uncurled BUE extrusion causes neither the secondary chip nor the notch wear. Therefore, optimization of the tool geometry to obtain a stable BUE extrusion is examined to suppress the notch wear.