Microstructure and properties of polycrystalline diamond with AlCoCrFeNi2.1 eutectic high-entropy alloys as binder

The performance of polycrystalline diamond (PCD) tools largely depends on the adhesion and catalyzing effect of the binder phase. In this study, AlCoCrFeNi2.1 eutectic high-entropy alloy (HEA) was used as a new binder material to synthesize the PCD samples. First-principles calculations showed that the interface strength between HEA and diamond is better than that between cobalt and diamond, suggesting that the HEA/PCD combination has the potential to exhibit better properties than the conventional cobalt/PCD tools. PCD samples with HEA as the binder phase were successfully synthesized using high-pressure and high-temperature conditions of 8.0 GPa and 1500-1700 degrees C. Several key performance indicators, including thermal expansion coefficient, Vickers hardness, transverse rupture strength, compressive strength, and wear resistance were measured to comprehensively evaluate the overall performance of the well-sintered HEA/PCD. The results showed that, compared with conventional cobalt/PCD, the HEA/PCD exhibited a lower thermal expansion coefficient and reduced graphitization of diamond at high temperatures above 920 K. HEA/PCD also demonstrated better mechanical properties than Co/PCD, including higher hardness, and greater transverse rupture strength and compressive strength. Moreover, over the same cutting distance against the granite block, HEA/PCD tools exhibited significantly lower wear loss than Co/PCD, indicating superior wear resistance. This study provides new insights and strategies for the design and optimization of PCD binders and PCD tools.