Liquid Phase Sintering of (Ti,Zr)C with WC-Co

Area of Science:

• Materials Science
• Powder Metallurgy
• Ceramics Engineering

Background:

• Sintering of composite materials is crucial for developing advanced ceramics and hard metals.
• Understanding the microstructural evolution during sintering is key to optimizing material properties.
• Ternary carbides like (Ti,Zr)C offer unique properties but their sintering behavior requires detailed investigation.

Purpose of the Study:

• To investigate the sintering behavior and microstructural evolution of WC-Co composites with (Ti,Zr)C.
• To compare the sintering process and final microstructure of (Ti,Zr)C-based composites with those using separate TiC and ZrC.
• To analyze the phase decomposition and grain formation during solid-state and liquid-state sintering.

Main Methods:

• Industrial sintering process with an isotherm at 1410 °C.
• Interrupted sintering trials to study intermediate stages.
• Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) for microstructural analysis.

Main Results:

• The (Ti,Zr)C phase decomposes into Ti-rich (γ₁) and Zr-rich (γ₂) nano-lamellae prior to liquid-state sintering.
• The final microstructure contains WC, Co binder, and two distinct γ phases (γ₁ and γ₂).
• γ₂ phase grains exhibit a core-shell structure with a (Ti,Zr)C core; carbide grain sizes are ~10% smaller in WC-(Ti,Zr)C-Co compared to WC-TiC-ZrC-Co.

Conclusions:

• The decomposition of (Ti,Zr)C significantly influences the final microstructure and sintering behavior.
• WC-(Ti,Zr)C-Co composites show distinct microstructural features, including core-shell structures and finer carbide grains.
• The study provides insights into controlling microstructure and properties in complex carbide-based composites through controlled sintering.