Thermodynamic calculations and construction of Ellingham and phase stability diagrams for the W-Ti-C-Co system

This study provides a thermodynamic analysis of phase equilibria and compound stability in the W–Ti–C–Co system using ab initio modeling, the Materials Project database, and HSC Chemistry 6. The focus is on identifying stable and metastable phases relevant to composite materials based on refractory metals and carbon with cobalt and titanium as alloying elements. Calculations yielded a list of characteristic phases, quaternary and ternary phase diagrams (Ti–W–C, Co–Ti–C, Co–W–C), Ellingham-type stability diagrams, and interfacial reaction maps. Mechanical properties were assessed via bulk and shear moduli, showing WC as the hardest and TiCo as the most ductile phase. The study predicts the likely formation of ternary carbides (W–Co, W–Ti), which strongly influence material properties. Fourteen interfacial reactions were identified, including carbide and intermetallic formation. Ellingham analysis showed Co2C is unstable above ~400°C, and Co7W6 is unfavorable at all temperatures, while WC remains stable up to ~1400°C, beyond which W2C dominates. These results deepen the understanding of phase behavior in multicomponent metal – carbon systems and support the development of thermally stable, mechanically optimized materials.