Structure and properties of CrN/DLC coating deposited by PVD ARC-cathodes and PACVD technology

Purpose: The main aim of the this research was the investigation of the microstructure and the mechanical properties of the CrN/DLC coating deposited by hybrid PVD/PACVD process onto the X40CrMoV5-1 hot work tool steel substrate. Design/methodology/approach: The microstructure of the investigated coating was observed on the scanning electron microscopy and transmission electron microscopy. Tests of the coatings' adhesion to the substrate material were made using the scratch test. A friction coefficient and the wear of coatings were determined in a test according to the ball-on-disk method. Findings: It was found that the microstructure of the CrN layer consisted of fine crystallites, while their average size fitted about 10 nm. The low-friction DLC show an amorphous character. The coating demonstrated a satisfactory adhesion to the substrate. The values of the critical load LC1 and LC2 of investigation coating account for, respectively, 9 and 39 N. In sliding dry friction conditions, after the break-in time, the friction coefficient for the investigated elements is set in the range between 0.03-0.06. The investigated coatings reveals high wear resistance. Practical implications: Economically efficient process improvement, increased production efficiency and quality and products reliability through increased durability and unfailing operation time of tools for plastic formation of non-ferrous metals and improved usable properties shall guarantee measurable economic effects to the manufacturers and users of the products. Moreover, it will enhance their competitiveness both on the domestic and overseas markets. Originality/value: The Author's original approach was the development of a double-layer coating within one process. Such coating consists of the internal hard PVD layer providing the appropriate hardness, strength, low thermal conductivity and restricting the impact of external factors on the wear process and the external low-friction layer providing good tribological properties.