Search

In this study, diffusion bonding of WC-Co cemented carbides to a tool steel was realized utilizing Ni foils as the interlayer in a vacuum. The effects of bonding temperature and Ni interlayer thickness on interfacial microstructure and mechanical properties of the joint were studied. The research results revealed that brittle phases and cracks were suppressed due to the Ni interlayer. Moreover, the coherent relationship of [1 2 0]WC//[1 0 1]Ni and (0 0 1)WC//(0 2 0)Ni was observed at the interface of WC grains and Ni interlayer, and it greatly contributed to the bonding strength of WC-Co/steel joint. As the bonding temperature increased, the atoms diffused sufficiently, and the interfacial defect dimensions decreased. Then, the Ni interlayer was transferred to solid solutions, resulting in the high shear strength of the bonded joint. The optimum shear strength (444.7 MPa) was achieved when the bonding was carried out at 1050 °C for 1 h with a 4-μm-thick Ni interlayer. The cracks were propagated in the interlayer and the WC-Co substrate near the bonding seam.

Microstructure transition and selection of Al2O3/Er3Al5O12/ZrO2 ternary eutectic ceramics with minimal eutectic spacing of 50 nm are studied by laser zone melting under rapid solidification rate. When the eutectic spacings are in micronscale, the ‘Chinese script’ structure is the main microstructure. As increasing the solidification rate (≥ 50 µm/s), the eutectic colony structure is obviously formed. The irregular-regular structural transition and coexistence are produced around eutectic spacing of 100–200 nm. The mechanism of irregular/regular eutectic structure transition and coexistence is revealed by considering the relative kinetic undercooling of each phase. In addition, the strong formation tendency of amorphous/nano-eutectic structure is observed at the surface of as-solidified ceramic drops by rapid liquid-metal quenching.