Research Study To Determine The Phase Equilibrium Relations Of Selected Metal Carbides At High Temperatures
Report Number: WADD TR 60-143 Part III
Author(s): Sara, R. V., Dolloff, R. T.
Corporate Author(s): Research Laboratory of National Carbon Company Division of Union Carbide Corporation
Laboratory: Directorate of Materials and Processes
Date of Publication: 1962-04
Pages: 37
Contract: AF 33(616)-6286
DoD Project: 7350
Identifier: AD0277794
Abstract:
The work here reported is the results of investigations of phase equilibria in the binary systems, tungsten-carbon and zirconium-carbon, A completed phase diagram for the tungsten-carbon system is presented which differs significantly from the one proposed by Sykes in 1930 and which is generally accepted today. A tentative phase diagram for the zirconium-carbon system is included, which, in general, resembles several versions published in the literature. The data were obtained by high-temperature differential thermal analysis and classical quenching procedures, both supplemented by metallographic, X-ray, and chemical techniques.Results for the tungsten-carbon binary system indicate eutectics between W and W2C at 2710°C and between W2C and β-WC at 2765°C. The W2C lattice accommodates 72 and 74 atomic per cent W at 2460° and 2710°C, respectively. Carbon solubility is evident only at 2525°C, the eutectoid temperature. The melting point of W2C was found to be 2795°C. WC is a line compound up to a peritectoid temperature of 2755°C. At 2755°C, WC decomposes into β-WC and graphite. A new cubic phase (β-WC) has been discovered which is stable only above 2525°C. This high temperature modification of WC, formed by a peritectic reaction at 2785°C, has a broad solubility range near the solidus.The zirconium-carbon system is characterized by eutectic temperatures of 1860° and 2850°C on the zirconium-rich and carbon-rich sides of ZrC, respectively. ZrC is the only carbide phase which has been observed in this system. ZrC, like most carbides with a face-centered cubic structure, has a broad solubility range. One terminal member corresponds to a composition containing 38.5 atomic per cent carbon at 1900°C. The carbon-rich member at this temperature, as well as the temperature dependence of solubility, is being evaluated by X-ray parametric methods. The phase change in zirconium saturated with carbon has been observed at 885°C by differential thermal analysis and at approximately 900°C by high temperature X-ray diffraction methods.
Provenance: IIT
Author(s): Sara, R. V., Dolloff, R. T.
Corporate Author(s): Research Laboratory of National Carbon Company Division of Union Carbide Corporation
Laboratory: Directorate of Materials and Processes
Date of Publication: 1962-04
Pages: 37
Contract: AF 33(616)-6286
DoD Project: 7350
Identifier: AD0277794
Abstract:
The work here reported is the results of investigations of phase equilibria in the binary systems, tungsten-carbon and zirconium-carbon, A completed phase diagram for the tungsten-carbon system is presented which differs significantly from the one proposed by Sykes in 1930 and which is generally accepted today. A tentative phase diagram for the zirconium-carbon system is included, which, in general, resembles several versions published in the literature. The data were obtained by high-temperature differential thermal analysis and classical quenching procedures, both supplemented by metallographic, X-ray, and chemical techniques.Results for the tungsten-carbon binary system indicate eutectics between W and W2C at 2710°C and between W2C and β-WC at 2765°C. The W2C lattice accommodates 72 and 74 atomic per cent W at 2460° and 2710°C, respectively. Carbon solubility is evident only at 2525°C, the eutectoid temperature. The melting point of W2C was found to be 2795°C. WC is a line compound up to a peritectoid temperature of 2755°C. At 2755°C, WC decomposes into β-WC and graphite. A new cubic phase (β-WC) has been discovered which is stable only above 2525°C. This high temperature modification of WC, formed by a peritectic reaction at 2785°C, has a broad solubility range near the solidus.The zirconium-carbon system is characterized by eutectic temperatures of 1860° and 2850°C on the zirconium-rich and carbon-rich sides of ZrC, respectively. ZrC is the only carbide phase which has been observed in this system. ZrC, like most carbides with a face-centered cubic structure, has a broad solubility range. One terminal member corresponds to a composition containing 38.5 atomic per cent carbon at 1900°C. The carbon-rich member at this temperature, as well as the temperature dependence of solubility, is being evaluated by X-ray parametric methods. The phase change in zirconium saturated with carbon has been observed at 885°C by differential thermal analysis and at approximately 900°C by high temperature X-ray diffraction methods.
Provenance: IIT