Microstructural evolutions and mechanical properties of TLP-bonded WC-Co/St52 with copper interlayer

In this research, the effect of different bonding times on the microstructure and mechanical properties of the WC-Co/St52 joint created by the transient liquid-phase process at 1200 & DEG;C using copper interlayer was investigated. For this purpose, bonding times of 1, 15, 30, and 45 min were used. The microstructure of the bonded samples was examined using an optical microscope as well as scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. Microhardness and tensile-shear strength tests were carried out to evaluate the mechanical properties of the joints. The results showed that there were two main zones of isothermal and athermal solidification in the bonding region, which determined the properties of the bonding samples. The isothermal solidification zone contained a Fe-rich solid solution, which increased its volume fraction with increasing the bonding time. The athermal solidification zone also contained a Cu-rich solid solution phase. The presence of Fe-rich solid solution in the centerline of the all joints caused the same hardness in all joints. The maximum tensile-shear strength was related to the sample with bonding time of 15 min, because of the proper continuity in the microstructure and presence of optimal amount of Cu-rich solid solution phase in microstructure.