Influence of high-rapid solidification of melt on structural characteristics of co-6tic alloy

The structure and properties of pure cobalt and the Co-6TiC alloy (mass %) produced by sintering the melt (HRMS) at 1150 °C and high-rapid solidification are compared. It is shown that cobalt, both after sintering (the initial state) and in the case of subsequent HRMS, contains, in addition to the equilibrium hcp-α-phase, a metastable fcc-γ-phase. In this case, the HRMS leads to an increase in the fraction of the nonequilibrium fcc-γ-phase from 27 to 55%. In the Co-6TiC alloy, after sintering and HRMS, a single-phase structure is formed, based on the metastable fcc-γ-phase. Calculations have shown that, after HRMS, the atomic volumes of the α- and γ-phases in cobalt are lower and in the Co-6TiC alloy are higher than in these materials in the initial (after sintering) state. The microhardness of Co-6TiC HRMS-fibers exceeds the one of cobalt fibers by more than 50% as a result of the double effect: stabilization of the fcc-γ-phase (it is inherent to TiC even at a normal crystallization rate) and increased distortion and fragmentation of the crystal lattice of the matrix and carbide particles as a result of HRMS.