The Distribution of Carbon in a Tungsten–Cobalt Alloy during Heat Treatment in a Gaseous Medium of Carbon Oxides
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Investigations of composition, structure, and hardness of ultrafine-grained solid alloy WC–8Co–0.4VC–0.4Cr3C2 after treatment in a gaseous mixture of CO + CO2 of compacts with a lack of carbon for 50 min at a temperature 650°C on the initial stage of liquid-phase sintering. It was found that at CO content of 72.5% in the gas mixture, conditions are created for replacing the initial carbon deficiency (about 0.3%) and obtaining two-phase ultrafine-grained carbide of stoichiometric composition, in which carbon and hardness are uniformly distributed over the depth of the samples. This alloy has the lowest porosity (2.5%) and the highest hardness (HV1941). It was found that an increase of up to 80% or a decrease of up to 0% of the CO content in a gas mixture leads to the formation of a lack of carbon (1.0%) or an excess of carbon (4.5%) on the surface of the samples. This leads to a significant decrease in hardness. It is shown that the change in the carbon content and hardness in the depth of the samples is much less than on the surface.
Keywords:ultrafine-grained tungsten-cobalt alloy hardness
The images on the scanning electron microscope were obtained in the Far Eastern Center of Electron Microscopy on the basis of the IBM FEB, Russian Academy of Sciences.
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