Interaction of yttrium barrier and calcium-rich phase on production and properties of WC precursor powders and alloys

摘要

In order to reduce or eliminate the adverse effects of calcium impurity, the interaction of Ca and rare earth Y co-doping on the preparation of WC-Co cemented carbides was investigated. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were employed to analyze the phase compositions, particle sizes and morphologies of them, respectively. The results show that the second type of "yttrium barrier effect" is observed and the adverse influence of Ca-rich phase on tungsten powder can be eliminated by it. The flexural strength and fracture toughness of YG6-0.01% Ca thorn 0.09%Y alloy are 2199.5 MPa and 11.49 MPa$m1/2, showing improvement of 6.5% and 2.7% compared to YG6 alloy, respectively. The evolutions of Ca-rich phase and Y-rich phase at the every alloy preparation stage of WO3, W, WC and cemented carbides are obtained. Furthermore, the strengthening mechanism of WC-Co cemented carbide with co-addition of Ca and Y is proposed.

关键词