Title

Research Study To Determine The Phase Equilibrium Relations Of Selected Metal Carbides At High Temperatures

Description

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.

Date

1962

Index Abstract

Contrails and DTIC condensed and truncated

Photo Quality

Incomplete

Report Number

WADD TR 60-143 Part III

Creator

Sara, R. V.

Dolloff, R. T.

Corporate Author

Research Laboratory of National Carbon Company Division of Union Carbide Corporation

Laboratory

Directorate of Materials and Processes

Extent

37

Identifier

AD0277794

AD0277794

Access Rights

OTS

Distribution Classification

1

Contract

AF 33(616)-6286

DoD Project

7350

DoD Task

None Given

DTIC Record Exists

No

Distribution Change Authority Correspondence

None

Report Availability

Full text available

Date Issued

1962-04

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

Lockheed Martin Missiles & Fire Control

Type

report

Format

1 online resource (v, 31 pages) : ill.

Subject

Ceramic Materials

Eutectics

High Temperature

Phase Studies

Temperature

Publisher

Wright-Patterson Air Force Base, OH : Directorate of Materials and Processes, Aeronautical Systems Division, Air Force Systems Command

Distribution Conflict

No