Facile Synthesis of High Entropy Carbide-based Cermets

Promovendus/a: Zahid Anwer

Promotor(en): Prof. dr. ir. Jozef Vleugels, De heer Shuigen Huang

This PhD focuses on developing innovative high-entropy carbide (HEC)-nickel (Ni) based cermets in a fast and cost-effective manner to realise HEC-Ni based cermets at large scale production. Using a single-step heating process, I successfully synthesized both equimolar and non-equimolar HEC-Ni cermets. The materials were prepared using commercially available monocarbide powders or a mix of transition metal oxides and graphite. During sintering, I discovered that certain carbides like TaC and NbC help form a solid solution at lower temperatures, with full densification occurring at around 1420°C. This process resulted in a unique composition gradient within the HEC phase, featuring a core-rim structure. Additionally, using softer, nano-sized transition metal oxides and graphite as starting materials led to HEC-Ni cermets with a more uniform grain structure and enhanced hardness. This improvement was due to the formation of pure carbide and binder phases during the carbothermal reduction process. The partial replacement of WC with Mo2C not only increased the solid solubility of hexagonal carbides (WC, Mo2C) but also resulted in finer grain sizes and distinct microstructures. Carbon content played a crucial role in controlling the microstructure and properties of the cermets. My experiments, supported by thermodynamic simulations, revealed that HEC-Ni cermets could maintain desirable properties over a broad range of carbon contents, making them less prone to unwanted secondary phases. To assess the practical applications of HEC-Ni cermets, I tested their resistance to high-temperature oxidation and wear. The results showed that HEC-Ni cermets developed a pseudo-protective oxide layer, providing appreciable oxidation resistance, especially at 700°C. They also exhibited promising wear resistance at high temperatures, outperforming traditional materials like WC-Co and NbC-Ni.

In summary, my research demonstrates that HEC-Ni cermets are a promising material for high-temperature applications due to their superior oxidation and wear resistance. These findings pave the way for further development and potential use of HEC-Ni cermets for wear-resistant applications.