Bias voltage optimum adjustment considering coatings' strength and adhesion requirements when cutting various steels

PVD coatings were deposited at various bias voltages on cemented carbide inserts. The coating's mechanical properties, fatigue and adhesion were determined via FEM-supported evaluation of nanoindentation, perpendicular and inclined impact test results. The coated inserts were applied in milling hardened and normalized steel. For explaining the wear evolution based on the cutting loads and stress fields developed in the coating and its substrate, FEM calculations were performed considering among others the films' strength and adhesion. According to the workpiece properties, certain coating's parameters become prevailing for the tool life. These depend on the bias voltage and facilitate its optimum adjustment.