Mechanical properties and microstructures of hybrid ultrasonic resistance brazing of WC-Co/BeCu

Cemented carbide (WC-15 wt.%Co)/beryllium bronze (BeCu) brazed with Ag-based filler was conducted by using a hybrid ultrasonic resistance brazing method. Based on microstructural analysis (nondestructive and cross-sectional observation) and mechanical evaluation (shear and hardness test), when hybrid ultrasonic vibrations with a frequency of about 30 kHz, it was shown that, not only the well-brazed area of the brazing joint interface increases more than 35% (up to 85%), resulting in that the shear strength increases 40% (about 241 MPa), but also the softened region of the BeCu foil is preserved within the contact area with the WC-Co bar, resulting from restraining the grain growth in the BeCu foil through deceasing the heat input and the high temperature residence time. Due to the acoustic cavitation and the acoustic streaming effects, robust brazed joints of dissimilar alloys or materials could be realized successfully even with no flux, and the properties of the base materials can be sustained as much as possible.