Abstract：To address the softening failure of the binder phase in cemented carbides under harsh deep-earth service conditions, a novel γ′ phase-strengthened WC-25Co-25Ni-3Al-9.05ZrC/8.54HfC cemented carbide was designed and fabricated in this study using the calculation of phase diagram method. Guided by calculation of phase diagram and integrated with key experimental characterizations, the microstructural evolution of the γ′ precipitates and their structure-property relationships with hardness were systematically investigated. The results show that the as-sintered sample can form a highly supersaturated matrix after solution treatment at 1 150 ℃, providing a strong driving force for the precipitation of γ′ phase during subsequent aging. As the aging temperature and time increase, the γ′ phase evolves from spherical particles to regular cubes, exhibiting directional alignment and Ostwald ripening at 800 ℃. Compared to the ZrC-added samples, HfC particles effectively inhibit discontinuous precipitation through the grain boundary pinning effect. The solution treatment at 1 150 ℃ combined with the 700 ℃ aging process constitutes the optimal window for hardness of the alloy. Among the samples, the WC-Co-Ni-Al-ZrC alloy achieves the highest hardness (HV10) of 717.3, while the WC-Co-Ni-Al-HfC alloy reaches a peak hardness (HV10) of 643.6. This study significantly enhances the hardness of WC-Co-Ni-Al-based cemented carbides through microstructure regulation, providing a theoretical basis and technical support for the design of cemented carbides for extreme deep-earth environments.
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2026, Vol. 31 
