Interfacial binding and heterogeneous nucleation mechanisms of HfC/HfO2 in HfO2/DZ125 composites: Insights from first-principles calculations and experiments

Abstract

In this paper, the interfacial bonding strengths of the precipitated phase (carbides) and addition phase (HfO2) in the DZ125 nickel-based superalloy, as well as the nucleation potential of carbides with HfO2 as a heterogeneous substrate, were calculated by first-principles calculations. Results show that the mismatches of HfC(011)/HfO2(011) and HfC(111)/HfO2(011) satisfy the semi-coherent relationship.Adhesion work (Wad) and interfacial energy were computed for six interfacial structures with varying terminations and stacking sequences. Model 3 in HfC(111)/HfO2(011) exhibited the highest Wad (6.67 J/m2), with an interfacial spacing of 0.95 Å and interfacial energy ranging from −3.2–1.81 J/m2, indicating the strongest interfacial bonding strength. Electronic structure analysis confirmed that the strong bonding in Model 3 is due to the formation of a robust Hf-C covalent bond at the interface. Uniaxial tensile tests revealed that Model 3 has a broad strain range and high tensile strength, with the Hf-C bond maintaining its integrity without fracture. Model 3, the most stable structure, supports the adhesion and growth of HfC on HfO2. The experiment confirms that HfO2 can serve as a heterogeneous nucleation site for HfC and contribute to the refinement of HfC grains.