Dissimilar vacuum brazing of cemented carbide to steel using double-layer filler metals

In the present paper, vacuum brazing of WC-Co/steel dissimilar joints was investigated using Cu/Ni-Cr-Fe-B double-layer filler metals. For this purpose, the specimens were brazed at 1200 degrees C for different holding time. Then, the microstructure and mechanical properties of the joints were studied. In addition, the wettability of WC-Co by the nickel-based alloy was evaluated, and it revealed the suitable wettability of the cemented carbide by this filler alloy (especially with higher brazing time). According to the shear test results, with an increase in the brazing time, the shear strength was decreased. The highest shear strength was obtained for the brazing time of 5 min ((similar to)413 MPa). The microstructural observations and XRD analysis showed that the joint region includes austenite and copper-rich solid-solutions. By increasing the brazing time from 5 min to 15 min, the width of the austenite layer in the WC-Co side was increased. Considering the higher yield strength of austenite phase compared to that of the low-hardness copper solid-solution, it seems that the decrease in the shear strength with an increase in the time is due to a reduction in the release of the residual stresses.