Design of metal-cutting tool coatings at the atomic level

Abstract

The research aims to lower tooling costs by reducing the time allotted to designing coatings on domestic cemented carbide metal-cutting tools by using the atomic force approach. The object of the study is coatings on cemented carbides of the tungsten carbide group such as titanium carbide (TiC), titanium nitride (TiN), and titanium (Ti) coatings or a nitride-based titanium, chromium and aluminum (Ti,Cr,Al)N composite coating. To select the most rational coatings, the article employed the method of calculating the functionals of interatomic systems using the density functional description of single atoms. The simplest measure to reduce the cost of designing metal-cutting instruments for manufacturing parts made of difficult-to-machine materials is to develop coatings for this tool type. The article considers various atomic arrangements in the coating material in relation to the WCo8 cemented carbide (VK8, tungsten carbide-cobalt alloy containing 8% cobalt). The calculated values of the interaction energy of the coating material atoms with one another and with the cemented carbide material ranged from 3.04 to 3.5 J/m2. Moreover, the research has established a correlation between the calculation results and the performance parameter of metal-cutting tools considering fracture toughness K1c (MPa ∙ √m). The main result of the study is that the employed computational method made it possible to determine the adhesion value for the atoms of the above-mentioned coating materials with tungsten carbide and cobalt atoms packed in different scale configurations. This enables the classification of coatings from the perspective of ensuring maximum performance properties of the tooling material. The present article assumes that the higher the adhesion value, the better the performance properties. The hypothesis has been confirmed experimentally as well as by the values of fracture toughness K1c. Thus, the most rational coating options have been selected for specified operating conditions of a metal-cutting tool, which permits reduction of tool design costs and makes it possible to predict the performance properties of tools at the design stage.