Study of degradation mechanism of metal-cutting tools and their hardening by ZrN PVD coatings

The wear behavior of packaging knives made from high-alloy steel of X205Cr12KU type used in wrapping machines of MC1DT-T type (MC Automations, Italy) has been investigated. ZrN nanostructured coatings deposited by physical vapor deposition (PVD) with RF discharge mode have been employed to act as protective coatings on such knives due to their high hardness and chemical stability. The chemical composition, microstructure, and physical-mechanical characteristics of the ZrN coating have been studied by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and nanoidentation method. The maximum nanohardness of the ZrN coating reached 32.05 GPa, which was 3.4 times higher than the tool matrix and was 57.65 % higher than that of the base metal spec-carbide phase. The application of coatings allowed stabilizing the working surface layer under deformation and to prevent the carbide phase from being crushed. Due to ZrN coating an increase in wear resistance by 3 times under production conditions was achieved.