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This study analysed and discussed the friction and wear properties, as well as the interface evolution behaviour of polycrystalline diamond compact (PDC) under various base oils, through conducting friction experiments on PDC/Si3N4 with different base oils. The friction and lubrication mechanism of PDC under different base oils were examined using scanning electron microscopy (SEM), x‐ray energy dispersive spectrometry (EDS), three‐dimensional white light interferometry, and Raman spectroscopy. The results of the study demonstrated that PDC exhibited the best friction and wear performance when lubricated with synthetic oil PAO, followed by castor oil. The inferior performance of paraffin oil can be attributed to its low viscosity, resulting in a lower presence of ions capable of passivating the carbon dangling bond. Consequently, paraffin oil displayed inadequate oxidation stability and increased susceptibility to oil film destruction, ultimately leading to suboptimal friction and wear characteristics. Overall, this study provides valuable insights for industrial applications, aiding in the selection of appropriate base oils as cutting fluids for PDC cutting tools and enhancing the friction and wear properties of PDC. [ABSTRACT FROM AUTHOR]

Turbo-drill is subjected to harsh working condition where drilling fluid, impact loads and high speed can cause thrust ball bearing raceway surface to quickly fatigue failure. Based on the Dang Van multi-axis fatigue evaluation criteria, the finite element model for raceway surface fatigue analysis was established, the fatigue usage factor under periodic loading was obtained. The results demonstrated that when the hardened layer thickness was larger than 0.4 mm, the fatigue usage factor had a dramatic reduction, thicker hardened layer thickness can significantly reduce the risk of raceway surface fatigue failure. Under the normal working condition of turbo-drill, the larger axial load can lead to a significant increase in fatigue usage factor, the axial load and hardened layer thickness have no influence on the maximum equivalent plastic strain, but they can remarkably change the maximum Mises stress. Therefore, the reasonable axial load and hardened thickness can improve the fatigue life of thrust ball bearing. [ABSTRACT FROM AUTHOR]

In harsh drilling conditions (e.g. abrasive drilling fluid), turbo-drill thrust ball may suffer from raceway surface indentation under the high axial load. The indentation can cause early failure of the bearing components. This paper establishes a micro-scale finite element model (FEM) to discuss the raceway surface indentation resulted from solid particle. For the sake of simplicity, the interaction between steel ball and solid particle as the latter is pressed into the raceway surface was depicted by axial and circumferential displacements. The distribution of stress and strain in solid particle and raceway surface was obtained from the finite element analysis. Through the discussion on solid particle ellipticity and the effect of friction coefficient on indentation features, it is learned that the variation in ellipticity has a slight impact on indentation depth, but a marked effect on raceway surface deformation; the friction coefficient has a significant impact on indentation edge shape and bottom centre of indentation. The simulation results provide a valuable reference for prevention of bearing raceway indentation. [ABSTRACT FROM AUTHOR]

Deep and ultra-deep well drilling is very common in petroleum industry. With the deepening of strata, downhole problems become more complex, and safety accidents become more frequent, which puts forward higher requirements for drilling fluid quality. At present, solid control system design is lack of rationality, and the technical properties have fallen behind, making it unable to reach the desired effect that the drilling fluid solid control, recycling of weighting agent, and the processing of oil-based drilling fluid. By analyzing the characteristics of the drilling fluid solid phase particles, combined with ultra-deep strata characteristics and the existing solid control equipment configuration and the using problem in domestic oil fields, the rational allocation of solid control system satisfying the ultra-deep well requirements was discussed. The optimized solid control system increased the solid control efficiency, and achieved the bidirectional recovery of weighting agent and drilling fluid. The idea provides references for the rationality improvement of solid control system configuration. [ABSTRACT FROM AUTHOR]