OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 1 2022 Introduction One of the methods for improving the performance of parts and components is to cover its elements with coatings that have higher physical, mechanical, and chemical properties than the base metal. A rational choice of the coating composition, deposition technique and conditions will determine the properties of the coatings and characteristics of the improved products. Modern technologies allow synthesizing coatings from multiple chemical elements in order to combine its different physical, mechanical and chemical properties in one coating. This is most often done through the formation of multilayer coatings with thin nanostructured layers [1]. The alternating layers provide an effective combination of various functional properties such as wear resistance, corrosion resistance, high hardness, etc. in one coating. Therefore, the choice of the composition of each layer will determine the resulting performance characteristics of the product. The most effective approach to the formation of multilayer coatings implies the deposition of one layer with high hardness and the other with the ability to absorb strain energy. This combination gives a coating with high hardness but not prone to brittle fracture at large strains, which is a desired goal of modern technology [2]. An important aspect is that modern types of equipment operate in high-power modes with high operating temperatures at which coatings must retain its properties. Thus, the high temperature resistance is also a necessary coating property in addition to the already mentioned ones. Chromium and zirconium nitride coatings correspond in some respects to the above requirements. It is known that ZrN coatings have high wear resistance and can effectively absorb mechanical strain energy during friction [3–8]. A single-layer CrN coating has low wear resistance due to columnar structure [9–12], while a multilayer coating of the same material has a much higher wear resistance [13–17], indicating a high structural sensitivity of the given material. Both of these types of coatings have high thermal stability and chemical resistance [14, 18]. Therefore, by alternating ZrN and CrN layers it is possible to obtain ZrCrN coatings with high physical and mechanical properties. Multilayer ZrCrN coatings can be applied by various methods [19]. The most widely known PVD techniques aremagnetron sputtering [20–25] andvacuumarc evaporation [26–30].The lattermethodprovides high adhesion between the coating and the substrate, and allows fl exible control over the composition and thickness of the deposited layer due to a wide-range variation of the energy of condensed ions. The literature reviews in [29, 30] indicate that the hardness of multilayer ZrCrN coatings deposited on TiC substrates strongly depends on its deposition conditions and, as a rule, does not exceed 30 GPa. A higher hardness (up to 42 GPa) was achieved in nanostructured multilayer ZrCrN coatings deposited on corrosion-resistant steel 12Cr18Ni10Ti [27]. Consequently, the substrate strongly affects the fi nal application properties of the coating. As far as we know there are no reports on multilayer ZrCrN coatings deposited on VK8 alloy, which is widely used for industrial metal forming and cutting tools. The purpose of this work is to study the structural-phase state and mechanical properties of ZrCrN coatings deposited by plasma-assisted vacuum arc evaporation on VK8 alloy substrates. Research methods Coatings were deposited by vacuum arc plasma evaporation. In the experiment, metal plasma was generated using two electric arc evaporators with 80-mm-diameter cylindrical cathodes made of E110 Zr alloy and 99.9% purity Cr. Gas plasma was generated by a plasma source with a thermionic and hollow cathode. The gas plasma source was used for cleaning, heating and chemical activation of the sample surfaces by gas ion bombardment, as well as for additional gas ionization and plasma-assisted coating deposition. VK8 hard alloy samples with a diameter of 10 mm and a thickness of 7 mm were mounted on a rotating planetary substrate holder at a distance of about 20 cm from the chamber axis at the exits of the plasma sources. Before the start of the experiment, the vacuum chamber with dimensions of about 650x650x650 mm3 was evacuated to a limiting pressure of 10-2 Pa using a TMP1000 turbomolecular pump. Argon plasma gas
RkJQdWJsaXNoZXIy MTk0ODM1