Effect of Bonding Temperature on Microstructure and Mechanical Properties of WC–Co/Steel Diffusion Brazed Joint

Abstract

In this work, the diffusion brazing of AISI 4145 steel to WC–Co cemented carbide using RBCuZn-D interlayer with bonding temperature values of 930, 960, 990 and 1020 °C was studied. The microstructure of the joint zone was evaluated by scanning electron microscope (SEM) and X-ray diffraction (XRD). Vickers microhardness and shear strength tests were performed to investigate mechanical behaviors of the brazed joints. The XRD and SEM results indicated that with increase of bonding temperature, the elements readily diffused along the interface and formed various compounds such as γ, α and β and Co3W3C. The results also showed that with the increase of bonding temperature from 930 to 960 °C, a sound metallurgical bond was produced, however in higher bonding temperatures (990 and 1020 °C) a decrease in mechanical properties of the joints was observed which could be due to the excessive zinc evaporation, interface heterogeneity and voids formation. The maximum shear strength of 425 MPa was obtained for the bond made at 960 °C.