Effect of cobalt content on the microstructure, microtexture, and mechanical properties of W-Ni-Fe-xCo alloys during solid-phase-sintering and liquid-phase-sintering

Abstract

Compared the effect of Co content on the microstructure, microtexture, and mechanical properties of W-Ni-Fe-xCo alloys during solid-phase-sintering and liquid-phase-sintering. The results indicated there is a non-uniform distribution of W and γ phases, accompanied by the presence of little voids during solid-phase-sintering at 1420 °C. Adding Co element enhances the wetting between the W and γ phases, and reduces the liquid-phase-sintering temperature, shrinking the size and quantity of pores. The W phase transforms into ball-shaped particles with completed liquid-phase-sintering at 1440 °C. With increased Co content, W grain size decreases, matrix fraction volume increases, and Cw-w continuity and dihedral angle decrease. The mechanical properties of the alloys improve with sintering temperature and Co content, the tensile strength and elongation reached 989 MPa and 13.7% due to the elimination of holes and the W content increased within γ phase. The relationship among W content in γ phase, strength, elongation, and microhardness with Co content were revealed. The solution strengthening effect increases, which drives the co-deformation of W and γ phases, thereby increasing the strength and elongation. The addition of Co element and the atomic diffusion at high temperature made the fibre microtexture more concentrated.