金刚石与磨料磨具工程2025，Vol.45Issue(6)：717-726,10.DOI:10.13394/j.cnki.jgszz.2025.0056
共晶高熵合金/聚晶金刚石复合材料的强韧化机制研究
Study on strengthening and toughening mechanisms of eutectic high-entropy alloy/polycrystalline diamond composites
摘要
Abstract
Objectives:Currently,most PDC cutters domestically and internationally use metallic cobalt(Co)as the binder.High-quality PDC products can be sintered under the conditions of a large six-anvil press(pressure≥5 GPa,temperature≥1 400℃).However,after extensive optimization by researchers,the material system of the PCD layer with traditional cobalt as the binder(Co/PCD)has gradually approached its design limits,making it difficult to further significantly improve the technical performance of PDC cutters.Although cobalt promotes D-D bonding during high-pressure and high-temperature sintering,its relatively low oxidation resistance and poor high-temperature stability lead to intergranular cracking and mechanical property degradation in PCD materials under extreme working conditions.Meanwhile,PCD materials bonded with transition metals,carbides,or carbonates exhibit promising potential in key in-dicators such as hardness and thermal stability,but their inherent characteristics limit the overall performance of PCD materials.Therefore,it is necessary to develop novel binder systems to break through the performance bottlenecks of traditional PCD materials.To this end,this study explores the regulatory mechanisms of eutectic high-entropy alloy(EHEA)as binders on the microstructure and properties of PCD materials,aiming to facilitate the development of new ultra-hard composites with high hardness,high toughness,and excellent thermal stability.Methods:Spherical Al-CoCrFeNi2.1 eutectic high-entropy alloy powder with an average particle size of 25 μm is used as the binder.Fine dia-mond powder with a primary particle size distribution of 0.8-1.4 μm is employed as the base material,and EHEA powder is added at volume fractions of 1%,3%,and 5%,respectively.The mixtures are uniformly blended using an agate mortar.The mixed powders are subjected to ultra-high-pressure and ultra-high-temperature sintering(15 GPa,2 000℃)using a 2 000-ton Kawai-type 6-8 multi-anvil press.The resulting PCD samples 1#(Diamond+1%EHEA),2#(Diamond+3%EHEA),and 3#(Diamond+5%EHEA)-are characterized using X-ray diffraction(XRD),scan-ning electron microscopy(SEM),and transmission electron microscopy(TEM)to analyze their phase composition and microstructure.Additionally,Vickers hardness testing and thermogravimetric analysis(TGA)are conducted to evaluate the hardness and thermal stability of the three samples.Results:Microstructural analysis reveals that the composite ma-terial consists of three characteristic regions:(1)a binder-free region with direct D-D bonding,(2)a diamond/EHEA in-filtration region formed through D-EHEA interfacial bonding,(3)a large-grain aggregation region where EHEA cata-lyzes diamond growth.The simultaneous enhancement of strength and toughness in the EHEA/PCD composite is achieved through synergistic toughening mechanisms,including plastic deformation-induced stacking faults/twinning structures,tortuous intergranular fracture paths,stress dispersion,crack deflection/termination by large diamond grains,and plastic deformation with stress buffering in EHEA-rich regions.Thermal stability tests demonstrates that the sintered sample with 3%EHEA(Diamond+3%EHEA)exhibits the optimal balance between oxidation resistance and thermal decomposition temperature,with an initial oxidation temperature of 761.6℃and a thermal decomposition tem-perature as high as 869.0℃.Conclusions:This study innovatively employs fine-grained diamond powder as the raw material and adopts EHEA as the binder to fabricate EHEA/PCD composites with varying binder volume fractions un-der ultra-high pressure and high-temperature conditions(15 GPa,2 000℃).The integrated strengthening and toughen-ing mechanisms of the EHEA/PCD composites stem from the synergistic effects of three characteristic structural re-gions:(1)Region A#ensures strength and toughness through stable D-D interfacial bonding and plastic deformation-in-duced stacking faults/twinning structures;(2)Region B#enhances toughness via strong D-EHEA interfacial bonding and the high plasticity/toughness of the infiltrated EHEA network,achieved by torturing intergranular fracture paths and mitigating localized stress concentration;(3)Region C#further suppresses crack propagation through crack deflection/termination by large diamond grains,coupled with plastic deformation and stress buffering in EHEA-rich zones.The three regions collectively enable simultaneous improvements in strength and toughness via dislocation strengthening,interfacial energy optimization,crack path complexity,and multi-stage energy dissipation.Moreover,the incorporation of EHEA ensures excellent thermal stability of the composites.In summary,EHEA exhibits significant potential to replace Co as a PCD binder,where microstructure regulation and multi-mechanism synergy are pivotal for enhancing composite performance.The EHEA/PCD composites provide valuable insights for developing next-genera-tion ultra-hard rock-breaking materials.关键词
聚晶金刚石/共晶高熵合金/显微表征/强韧化机制/热稳定性Key words
polycrystalline diamond(PCD)/eutectic high-entropy alloy(EHEA)/microstructure/strengthening and toughening mechanism/thermal stability分类
数理科学引用本文复制引用
李凤娇,史春燕,高德利,韩欣,刘靖靖,骈小璇,梁述举,刘维..共晶高熵合金/聚晶金刚石复合材料的强韧化机制研究[J].金刚石与磨料磨具工程,2025,45(6):717-726,10.基金项目
国家工信部专项(ZX20240310) （ZX20240310）
国家自然科学基金(52574016,52394250,52234002) （52574016,52394250,52234002）
国机集团重大科技专项(ZDZX2024-09). （ZDZX2024-09）
