Abstract
In the present work, phase relationships in the Mn- and Co- rich regions of the Mn-Co-C system have been investigated at 1173 and 1273K by using an equilibration technique. Alloys of Mn-Co-C were prepared from ultra pure Mn, Co and C powders by mixing the components in required ratios and melting the mixtures in an induction furnace. The melted samples were placed inside quartz capsules and sealed under vacuum. The samples were then placed in the even temperature zone (±0.15°C) of a vertical furnace and heat treated. The duration of the heat treatment was 14 days at 1173K and 7 days at 1273K. The samples were quenched in water after heat treatment. The phase identification of the heat treated samples were carried out by SEM (Scanning Electron Microscope), and the chemical analyses of the various phases present were obtained by the EDS (Electron Dispersion Spectroscopy)-detector attached to the SEM-unit.
On the basis of the present results and the phase diagram information for the three binary systems available in literature, the major part of the Mn-Co-C phase diagram at 1173 and 1273K has been constructed. The results indicate that β-Mn, γ-Mn and α-Co solid solutions exist over appreciable ranges of composition, and cubic (Mn, Co)23C6, hexagonal (Mn, Co)15C4, monoclinic (Mn, Co)5C2 as well as hexagonal (ortrigonal) (Mn, Co)7C3 occur essentially as line compounds. The various two- and three phase regions existing in this system at the temperatures in question are mapped and the isothermal sections are presented.
