碳纳米管对PDC热稳定性及力学性能的影响

Effect of carbon nanotubes on thermal stability and mechanical properties of PDC

摘要:

由于现代石油、煤田开采的环境愈加复杂，对钻头的耐热性与抗冲击韧性提出了更高的要求。而聚晶金刚石复合片(PDC)作为钻头工作的核心零部件，会直接影响钻头的使用寿命。在实际的工况中，PDC往往会以断裂和耐热性差的形式失效。碳纳米管具有优异的力学性能、化学稳定性和热稳定性，将碳纳米管引入PCD层中，可以解决PDC中抗冲击韧性差、热稳定性差的问题。本研究采用碳纳米管作为PDC的增强相，在高压和高温(5.5 GPa和1300°C)的条件下制备PDC复合材料，烧结时间为90 s。对PCD复合材料的微观结构、元素分布、相组成进行了表征，分析了碳纳米管对复合材料力学性能和热稳定性的影响。研究结果表明，碳纳米管添加量为1.4 wt%的PDC抗冲击韧性从400 J提升到550 J，比原始PDC的抗冲击韧性高37.5%，PCD复合材料抗冲击韧性的提高归因于碳纳米管在裂纹偏转过程中的拔出和桥接。碳纳米管添加量为1.6 wt%的PDC耐热性从原始的704℃提高至813℃，摩擦系数从0.064降低到了0.048，磨耗比达到159.69×104，比原始PDC提高了59.64×104。

Abstract:

The higher requirements are proposed for the thermal stability and impact toughness of drill bits due to the increasingly complex environment of modern oil and coal mining. Polycrystalline diamond composite sheet (PDC) is the core parts of the drill and has a direct impact on the service life of the drill. The PDC always fail in actual working conditions owing to poor thermal stability and fracture. Carbon nanotubes have excellent mechanical properties, chemical stability and thermal stability. Carbon nanotubes are introduced into PCD layer can solve the problems of poor impact toughness and poor thermal stability in PDC. In this study, carbon nanotubes were used as the reinforcing phase and added into PDC. PDC composites were prepared under high pressure and high temperature (5.5 GPa and 1300℃), and the sintering time was 90 s. The effects of carbon nanotubes on mechanical properties and thermal stability of PDC composites were analyzed, the microstructure, element distribution and phase composition of PCD composites were characterized. The results show that the impact toughness of PDC with 1.4 wt% carbon nanotubes increased from 400 J to 550 J, which is 37.5% higher than that of original PDC. The increase of PCD composites impact toughness is attributed to the removal and bridging of carbon nanotubes during crack deflection. The thermal stability of PDC with 1.6 wt% carbon nanotubes increased from 704℃ to 813℃, the friction coefficient decreased from 0.064 to 0.048. The wear ratio reached 159.69×104, which was 59.64×104 higher than that of the original PDC.