Effect of MoS2 element diffusion under high temperature condition on the tribological properties of cemented carbide materials

Abstract

To further clarify the effect mechanism of MoS2 element diffusion on tribological properties of cemented carbide materials, an investigation was carried in this study. The diffusion process between cemented carbide inserts and MoS2 powder under high temperature condition was carried out in a muffle furnace device. The surface morphology and chemical element content of test samples were observed and measured with scanning electron microscope, energy spectrum, and X-ray diffraction instruments. The kinetics of the diffusion process was quantitatively discussed by thermodynamic experiments. Tribological experiments were carried out using friction and wear machine with which the friction coefficient and wear scar were obtained. The experimental results show that high temperature has a significant effect on physical and mechanical properties of cemented carbide materials. Moreover, MoS2 elements diffusion on sample surface is existed and induced by thermal action, which results in a further changing of material properties of cemented carbide. The WC grain growth is inhibited when molybdenum element is only infiltration on sample surface at 500 °C, which improves the surface morphology and hardness of test sample. However, the oxidation rate, friction coefficient, and wear rate of test sample are the highest when heating temperature larger than 500 °C. The main reason is that, as the temperature increasing, the diffusion of sulfur elements is occurred and intensified the loss of cobalt element on sample surface. So, the bonding ability of it is decreased due to the loss of bonding phase Co. Thus, the surface hardness and wear resistance of test sample is deteriorated. This study provides a theoretical foundation for the application of molybdenum disulfide in tool cutting lubrication condition.