Stability domains of (Ti,W)C and (Ti,W)(CN) during carbothermal reduction of TiO (2)/WO3 mixture at 1500 K

Abstract

Phase stability diagrams for the carbothermal reduction of a mixture of TiO2 and WO3 at 1500 K were constructed as a function of the carbon activity, oxygen pressure and characteristics of solution formation. Through this, it was found that the stable domains of carbides/carbonitrides, including (Ti,W)C/(Ti,W)(CN), are larger than the phases that are formed when solid-solution phases are not considered due to their greater stability. The use of a nitrogen atmosphere instead of vacuum expanded the stable domains of the solid-solution phases, indicating that they are made more stable under these conditions. Using these stability diagrams, the reaction sequence of carbothermal reduction can be predicted, and so this study can provide a guideline for preparing tougher carbide/carbonitride (Ti,W)C/(Ti,W)(CN) phases from TiO2/WO3 mixtures. (C) 2016 Elsevier Ltd. All rights reserved.