Qualification of PVD Coatings for Machining Using a Planing Test Setup

During machining of steel, adhesive and abrasive wear appear as damage mechanisms of the tools. Thin hard coatings deposited by physical vapor deposition for wear protection of cutting tools are state of the art. For the present article, three different coating systems CrAlN+Mo:S, TiAlCrSiN and CrAlON are investigated using a planing test setup. For this purpose, a planing test rig was used, which is equipped with a simultaneous measuring system for the analysis of process forces and chip formation based on high-speed recordings. Coated cemented carbide tools were used for planing a 42CrMo4+QT workpiece. The oxynitride coating CrAlON showed a lower adhesion tendency against the steel workpiece material during planing compared to the nitride coatings CrAlN+Mo:S and TiAlCrSiN. This prevented adhesive wear and reduced friction of CrAlON. The reduced friction decreased the chip thickness during cutting. Moreover, CrAlON showed a reduced contact length.