Strengthening mechanism of cemented carbide containing Re

Abstract

In the present study, the microstructural changes of WC hard phase, phase transition of Cobalt (Co) in the binder and grain boundary characteristics were investigated to interpret the strengthening mechanism of the cemented carbides containing Rhenium (Re). As the content of Re increased, the mean grain size of WC decreased from 0.95 μm to 0.43 μm. Re promoted the martensite transition of Co phase from face-centred cubic structure (fcc) to close-packed hexagonal structure (hcp) by lowering the stack fault energies, which stabilized the hcp-Co. Meanwhile, the addition of Re weakened the concentration of textures {0001}, which indicated the preferred textures {0001} disappeared and promoted the isotropy of WC grains. The number of special grain boundaries (especially the big angle grain boundaries and coincidence site lattice (Σ = 2)) increased obviously after Re addition. With the increase of Re content, hardness and transverse rupture strength (TRS) rose rapidly. Cemented carbide with 6 wt% Re displayed the topmost hardness of 1648.4 HV30 and TRS of 3690 MPa. The wear rate of cemented carbide with 6 wt% Re was approximately one-fifth of cemented carbide without Re addition. The excellent hardness, TRS and wear resistance of the cemented carbides were attributed to the Re induced synergistic strengthening effect of grain refinement, phase transition and formation of special grain boundaries.