Study of stability of properties of nanostructural coatings on the nano- and micro level

Abstract

In this work the packaging knives made from high-alloy steel of X205Cr12KU type used in wrapping machines of MC1DT-T type (MC Automations, Italy) has been investigated. In order to increase the cutting tool operational stability, the hardening implementation is reasonable. The method is proposed for increasing the wear resistance of the surface working layer of tools by hardening nanostructured ceramic coating. Zirconium dioxide ZrO₂ ceramics
possesses high resistance to crack propagation, high fracture toughness, high thermal expansion coefficient (α = 11x10-6/K, similar to some types of steel) and due to these properties, it is very much suitable for joining ceramic and steel.
The ZrO₂ coatings were obtained in "Bulat" type device by condensing vacuum-arc plasma purified from macroparticulates by means of the curvilinear filter.
Comprehensive studies of the structure and mechanical properties of the ceramic coating have been carried out. Structure examinations – X-ray fluorescent analysis (XRF), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) with microanalysis (EDS), nanoidentation method – were performed to study phase and chemical composition, surface morphology, microstructure and nanohardness of coatings. Features of the components distribution in the coating at recommended processing parameters have been studied. SEM investigations revealed the formation of crack-free structure of the film. XRD data revealed the formation of fine-crystalline structured films with average grain size of ~25 nm.
The stability of the properties of the nanostructured ZrO₂ coating on the nano- and micro levels has been studied. Application of nano-coating helps to increase the micro- and nanohardness of surface of the cutting tool. Measurements of microhardness of the ceramic coating has been carried out under different loads of indenter: 0,245; 0,490; 0,98 N. The degree of vertical and horizontal heterogeneity was assessed by the anisotropy of the properties. Anisotropy of the properties was detected under a load of 0.245 N, which is associated with local heterogeneity in the distribution of the components of the substrate.
The nanohardness was measured by Nanoindenter G200 (USA). The maximum nanohardness of ZrО₂ coating comprised 13,78 GPa with the data spread 4,75 %. The high level of nanohardness of hardening ceramic coating allowed to increase the wear resistance of the working surface layer in operation and to increase the time between tool retooling.