Microstructural Evolutions and Mechanical Properties of Transient Liquid Phase Bonded WC-Co/St52 with BNi-2 Interlayer

In this study, the transient liquid phase bonding of St52 plain carbon steel to WC-Co compound using BNi-2 interlayer with a thickness of 50 μm was investigated. For this purpose, samples were bonded at a temperature of 1050 °C and holding times of 1, 15, 30 and 45 min. After the joining process, the microstructure of the bonded samples was examined using a scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. X-ray diffraction analysis was also used to investigate the effects of bonding parameters on the phase transformations of the bonding region. Microhardness and tensile shear tests were also conducted to study the mechanical properties of the bonded samples. Microstructural studies showed that the formation mechanism of the solidification zone in all samples was isothermal solidification mechanism. The results of the investigations showed that the only phase in the isothermal solidification zone was the nickel base solid solution. The maximum hardness in all samples belonged to WC-Co base materials due to the presence of WC particles in it. The maximum tensile-shear strength was related to the sample with bonding time of 30 min. The mode of failure in all samples was a combination of brittle and ductile fracture.