Tribological properties and dry machining characteristics of PVD-coated carbide inserts

摘要

Tools for cutting operation are subject to very high abrasive, adhesive, and thermal loads. Process security and preparation quality as well as a sufficiently high tool life demand for the development of hard coatings with reduced seizure tendency, high hot hardness, and increased wear resistance especially under dry machining conditions. TiAlN coatings are the state-of-the-art coatings for machining operations. Hard materials on chromium basis like CrN or CrAlN are preferably used for bending and stamping tools. Thus, these coatings could have a high potential in machining operations. The aim of using chromium-based coatings is to redirect the heat from the workpiece and tool into the chip, thus acting as a thermal barrier. Due to their high oxidation resistance, CrN and CrxAlyN coatings were deposited on WC/Co inserts. In order to find improved coatings for dry machining operations, mechanical characterizations and turning tests were performed. The characterization of the coatings includes fundamental properties such as thickness, hardness, and critical load. With Glow Discharge Optical Emission Spectroscopy (GDOES), depth profile analyses were executed. SEM analyses supplemented the picture of the scratch tests. Turning operations were performed in model tests to characterize the dry machining characteristics. The wear properties of CrN and CrxAlyN coatings were compared with industrially coated (Ti,Al)N carbide inserts. Calculations of the friction coefficient supplemented the tests.