Study on elemental composition and interfacial structure of the second phase in WC-8Co hard alloy doped with rare earth components

Y/Zr-doped tungsten(W) powders were prepared by chemical precipitation method and spray drying technology, which was used to modify WC-8Co cemented carbides. The composition and microstructure of the Y/Zr-doped powder and alloy was characterized. The second phase referred to the elements or compounds except the matrix in the Y/Zr-doped powder or alloy. The elemental composition and interfacial structure of the second phase in alloys were discussed in detail. The improvement mechanism of the interface structure between the second phase and the matrix on the alloy properties was analyzed. The results indicated that the components of the second phase in rare earth doped hard alloys were Y2O3 and ZrO2. There was good consistency between the crystal plane of Y2O3 and WC, which created a coherent interface relationship. A transitional interface structure was formed at the intersection of Y2O3 particles and WC grains. Due to the good interface relationship between Y2O3 and WC, as well as the transition interface structure, Y-doped WC-8Co hardmental exhibited the best performance, with hardness, fracture toughness, and transverse fracture strength(TRS) of 91.1 HRA, 13.8 MPa.m(1/2), and 2730 MPa, respectively.