熔盐法制备Mo2C镀层增强金刚石抗压性能机理研究

Mechanism of enhancing compressive properties of diamond by Mo2C coating prepared via molten salt method

摘要:

为提升金刚石单颗粒抗压强度，改善孕镶金刚石钻头在硬地层的钻进性能，本文采用熔盐法在金刚石表面制备碳化钼（Mo?C）镀层，通过SEM、XRD进行微观表征，测试单颗粒抗压强度，并利用有限元模拟分析镀层产生的残余热应力及其强化机理。结果表明：经1323 K保温90 min后，金刚石表面形成连续、致密的Mo?C镀层，平均厚度约2.38 μm；镀层后金刚石的单颗粒抗压强度由84 N提高至156 N，增幅达85.71%。有限元模拟显示，降温过程中因Mo?C与金刚石热膨胀系数差异，金刚石内部产生约445.6 MPa的残余压应力，该压应力在外部载荷作用下抵消裂纹尖端的拉应力，抑制裂纹萌生与扩展，从而显著提高抗压性能。本研究揭示了镀层增强金刚石抗压强度的热应力机制，为高性能金刚石钻头的设计与制造提供了理论依据和工程参考。

Abstract:

To improve the single-grain compressive strength of diamond and enhance the drilling performance of impregnated diamond bits in hard formations， a molybdenum carbide （Mo?C） coating was prepared on the diamond surface via the molten salt method. Microstructural characterization was conducted using scanning electron microscopy （SEM） and X-ray diffraction （XRD）， the single-grain compressive strength was measured， and finite element simulation was employed to analyze the residual thermal stress induced by the coating and its strengthening mechanism. The results indicate that after holding at 1323 K for 90 min， a continuous and dense Mo?C coating forms on the diamond surface， with an average thickness of approximately 2.38 μm. The single-grain compressive strength of the coated diamond increases from 84 N to 156 N， representing an increment of 85.71%. Finite element simulation reveals that due to the difference in thermal expansion coefficients between Mo?C and diamond during the cooling process， a residual compressive stress of approximately 445.6 MPa is generated within the diamond. Under external loading， this compressive stress counteracts the tensile stress at the crack tip， inhibiting crack initiation and propagation， thereby significantly improving the compressive performance. This study reveals the thermal stress mechanism for the coating-enhanced compressive strength of diamond， providing a theoretical basis and engineering reference for the design and manufacture of high-performance diamond bits.