Methodology of formation of multi-layered coatings for carbide cutting tools

In this paper, we consider the development of the methodology for the formation of nanostructured multi-layered composite coatings to improve the cutting properties of carbide cutting tools in the high-performance machining of various materials. The methodology for the formation of the composition, structure, and properties of developed composite coatings with a three-layered architecture was based on the phenomenological theory of the thermodynamic criteria for the evaluation of adhesion, and the assumption of the prevailing adhesion-fatigue wear of carbide cutting tools. The synthesis of coatings was carried out through filtered cathodic vacuum-arc deposition. The hardness, adhesion, and cutting properties of the developed coatings deposited on the carbide substrates were studied. It was found that the synthesized coatings had a nanoscale grain structure and thickness of sublayers, which significantly increased the area of intergranular and interlayer boundaries and provided a considerably balanced relation of the most important characteristics of the coating, such as "hardness-heat resistance". Such structures are characterized by increased toughness and resistance to the formation and development of "brittle" cracks and more efficient resistance to fractures in conditions of complex stress from external influences. It is revealed that, in the longitudinal turning of steel, carbide tools with the developed coatings demonstrated a tool life of five times higher than the tool life of uncoated tools and up to three times higher than the tool life of tools with standard coatings.