Annealing effect on the mechanical properties of ultrafine WC-Co materials

In dry machining, the tool-chip interface temperature is a critical factor affecting the engineering performance of WC-Co tools. As the temperature variation of the cutting tool in dry machining is similar to that in annealing process, the effect of tool-chip interface temperature on the mechanical properties of cutting tool materials in dry machining can be studied by means of annealing experiment. In this paper, a series of annealing experiments of ultrafine-grained WC-Co materials were conducted, and the effects of the annealing temperature and holding time on the mechanical properties of WC-Co materials, including flexural strength, hardness and fracture toughness, were investigated. The results show that under the experimental conditions, the annealing temperature dominates the mechanical properties of WC-Co materials. The flexural strength and fracture toughness of the ultrafine-grained WC-Co materials decrease in different extent with increasing of annealing temperature, whereas the hardness does not change obviously. The measurements of the microstructures and residual stresses revealed that the deterioration of mechanical properties of WC-Co materials after annealing can be attributed to the relaxation of compressive residual stress.