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

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.