Testing method of compressive force of polycrystalline diamond compact

ObjectiveIn practical applications, polycrystalline diamond compact (PDC) cutters primarily serve as the main cutting elements, enduring continuous compression, friction, and impact from geological formations. These forces often lead to wear, cracks, or fragmentation of PDC, resulting in rapid tool failure. The compressive force of PDC, defined as the maximum force it can withstand before fracture under external loading, is a critical mechanical parameter for evaluating its resistance to compressive failure and ultimate load-bearing capacity. However, current industry standards involve compressing the PDC face to induce fracture for determining its static compressive force. This method suffers from rapid pressure head wear, significant deviations from real-world loading conditions, and challenges in directly quantifying the compressive force of the polycrystalline diamond (PCD) layer. To simulate the compressive forces encountered during service and establish a robust quality evaluation system, this study investigates a novel approach to characterize PDC compressive resistance. MethodsYG6 cemented carbide spherical pressure heads with diameters of 24, 16, 10 mm are employed to apply compressive loads at both the center and quarter-diameter positions of 1613-type PDC samples. The critical fracture force, identified by a sudden load drop during PCD layer failure, is recorded as the compressive force. The effects of pressure head diameter and loading position on test results are systematically analyzed. 1916-type PDC pressure heads with varying surface hardness (41, 58, 72, 89 GPa) and surface roughness (Ra = 0.1, 0.8, 1.6 μm) are utilized to evaluate the compressive force of 1313-type, 1613-type, and 1916-type PDC samples. Angled fixtures (20°, 30°, 45°, 60°) and loading rates (1–10 mm/min) are applied to assess the influences of pressure head hardness, surface roughness, loading rate, and sample inclination. Repeatability tests and pressure head longevity trials are conducted to validate methodological accuracy. ResultsDuring the pressure process, the cemented carbide ball pressure head and the surface of the tested PDC sample change from point contact to surface contact. With the increase of the diameter of the cemented carbide ball pressure head, the contact area between the cemented carbide ball pressure head and the surface of the tested PDC sample increases, resulting in the reduction of the load per unit area on the tested PDC sample. Therefore, the compressive force of the PDC increases with the increase of the diameter of the metal indenter. However, when using the cemented carbide ball pressure head, the maximum service life is only twice, which is difficult to meet the needs of engineering testing. In addition, central loading produced compressive force values 1.4 times higher than edge loading, with fracture morphology differences: umbrella-shaped peeling fractures occurs under central loading, whereas asymmetric fractures appear at edge positions. The four key factors of hardness, surface roughness, loading rate of the PDC pressure head, and tilt angle of the tested PDC sample are studied. The optimal testing parameters are identified as PDC pressure head hardness ≥ 58 GPa, loading rate 1–5 mm/min, and PDC sample inclination at 20°, ensuring the test results stability of the PDC sample. PDC pressure head surface roughness (Ra = 0.1, 0.8, 1.6 μm) shows negligible impact on compressive force measurements of the PDC sample. Under the same test conditions, both intra- and inter-batch PDC samples demonstrates a coefficient of variation CV < 10%, meeting repeatability requirements. To reduce replacement costs of the PDC pressure head, when a fixed position of the PDC pressure head fails, the indenter can be rotated or moved to an undamaged position. Theoretically, its overall service life can exceed 10 times that of metal pressure heads through positional rotation after localized failure at fixed contact points. ConclusionThis study proposes a PDC-versus-PDC indentation method employing point-contact compression to rapidly determine compressive force. The protocol demonstrates operational simplicity and high repeatability, effectively addressing limitations of conventional metal pressure head approaches. By establishing correlations between pressure head properties, loading parameters, and fracture behavior, this method enhances the PDC quality assessment framework. The findings provide critical guidance for PDC performance optimization and quality control, advancing the development of standardized mechanical evaluation protocols for extreme-service cutting tools. Future work should focus on further study the internal relationship between the measured PDC compressive force and its impact resistance, wear resistance, and application performance, to evaluate its application performance through the PDC compressive strength, and provide reference for the actual drilling.