Elements in the carbide tool and workpiece material will diffuse during the cutting process, thus affecting tool life. To address the problem of diffusion wear on the rake face of the carbide tool, a cutting test scheme was proposed to analyze the heat and force conditions of element diffusion. A static clamping diffusion experiment of the tool and workpiece material was conducted to obtain diffusion data on the tool-chip element. Based on the analysis of element diffusion in the contact area of the tool-chip during the cutting process, the theoretical model of element diffusion in the tool was established using the Gaussian solution of Fick’s second law to determine the threshold value of the element concentration when the tool was damaged. The hardness of the tool surface was also measured and analyzed. The results showed that the wear depth of the rake face can be predicted using the established element diffusion model, whose results are consistent with the experimental findings. The element concentration on the crescent surface at the tool rake face remained constant under different cutting time, while the loss of W was more obvious. The experiments of the diffusion couple verified that element diffusion causes a decrease in the hardness of the tool surface, and tool hardness increases with greater distance from the bonding surface, which eventually reaches the hardness of the tool substrate. The research results lay a theoretical foundation for investigating the failure process of carbide cutting tools and predicting their service life.