Tool Wear Mechanism in Continuous Cutting of Hardened Tool Steels
Y K. Chou, Christopher J. Evans
Precision hard turning provides an alternative to grinding in some finishing applications. Rapid tool wear, however, remains an impediment to the process being economically viable. This experimental study investigates microstructural aspects of cubic boron nitride (CBN) tool wear in finish hard turning. Results indicate that; 1) carbide sizes of the workpiece have significant effects on tool wear; 2) flank wear rate can be correlated with mean carbide diameter of the workpiece; 3) wear resistance monotonically increases with decreasing CBN grain size; and 4) in finish turning with low CBN content tools, the governing wear mechanism is fine scale attrition by microfracture and fatigue. A powder metallurgy M50 bar hard turned using an ultrafine CBN grain tool shows flank wear less than 45 ?m VBmax after 6.2 km cutting distance; this wear rate equals 3.1 microm/km, over an order of magnitude lower than when machining conventional M50 under identical conditions. Surface finish is better than 80 nm Ra.
CBN tools, Hard turning, Manufacturing Processes, Tool wear, Tool wear