The Distribution of Carbon in a Tungsten–Cobalt Alloy during Heat Treatment in a Gaseous Medium of Carbon Oxides

Abstract

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.