Melting diagram of cobalt-rich alloys in the system C–Co–Nb

Chem. Met. Alloys 8 (2015) 83-90

https://doi.org/10.30970/cma8.0309

Galina DMITRIEVA, Tetyana CHEREPOVA

The melting diagram of cobalt containing up to 3 wt.% C and 40 wt.% Nb was investigated and the liquidus and solidus projections were determined. Alloys were prepared by arc melting and cast from the liquid state. No ternary phases were found. The investigated part of the C–Co–Nb phase diagram contains three isothermal three-phase planes, corresponding to the following four-phase invariant reactions with participation of liquid: L ↔ <Co> + NbC + C (1310°С), L ↔ NbC + <Co> + Co₃Nb (1230°С), L + NbC + Co₂Nb ↔ Co₃Nb (1430°С). The eutectic temperature for the quasibinary system Co–NbC was determined to be 1420±10°C for an optimal niobium to carbon ratio of 9.5 (wt.%) in the carbide (NbC_0.814).

Проекція поверхні солідус кобальтової частини системи С–Со–Nb: ○ – однофазні сплави, □ – двофазні сплави, ∆ – трифазні сплави,◊ – дані ЛРСА

Keywords

Cobalt / Niobium / Carbon / Melting diagram / Eutectic