Modeling of CBN Tool Flank Wear Progression in Finish Hard Turning

Cubic Boron Nitride (CBN) cutters are widely used in finish turning of hardened parts. Their wear mechanisms and associated wear rates are important issues to be understood in view of the high cost of CBN cutters and because of the tool change down-time cost which impacts the economic justification of CBN precision hard turning. The objective of this study is to present a methodology to analytically model the CBN tool flank wear rate as a function of tool/workpiece material properties, cutting parameters and process arrangement in three-dimensional finish hard turning. The proposed model is calibrated with experimental data of finish turning of hardened 52100 bearing steel with a CBN insert, and further validated over practical hard turning conditions. It is shown that adhesion is the main wear mechanism over common cutting conditions, which agrees with documented observations, however, chemical diffusion can gain dominance over extended periods of machining time under aggressive cutting conditions.