Search Results (174)

The high-efficiency polishing of large-sized polycrystalline diamond (PCD) wafers continues to pose significant challenges in its practical applications. Conventional mechanical polishing suffers from a low material removal rate (MRR) and surface damage. To improve the process efficiency, this study investigates the effect of chemomechanical abrasive polishing (CMAP) with a slurry containing high-concentration H₂O₂ and varying mass percentages of SiO₂ powder and diamond particles on surface morphology, surface roughness, material removal rate (MRR), and microstrain of PCD disks. The contributions of mechanical action, chemical action, and bubble cavitation to the CMAP process are analyzed. Scanning electron microscopy (SEM) observations indicate that large grains present in PCD are effectively eliminated after CMAP, leading to a notable reduction in surface roughness. The optimal results are obtained with 60 wt% SiO₂ powder and 40 wt% diamond particles, achieving a maximum MRR of 1039.78 μm/(MPa·h) (15.5% improvement compared to the mechanical method) and a minimum surface roughness (Sa) of 3.59 μm. Additionally, the microstrain on the PCD disk shows a slight reduction following the CMAP process. The material removal mechanism is primarily attributed to mechanical action (70.8%), with bubble cavitation and chemical action (27.5%) and action of SiO₂ (1.7%) playing secondary roles. The incorporation of SiO₂ leads to the formation of a lubricating layer, significantly reducing surface damage and decreasing the surface roughness Sa to 1.39 µm. Full article

The study investigates the problem of modeling cutting-force components through response surface methodology and reports the results of an investigation into the impact of machining parameters on the cutting mechanics of polymer–matrix composites. The novelty of this study is the modeling of cutting forces and the determination of mathematical models of these forces. The models describe the values of forces as a function of the milling parameters. In addition, the cutting resistance of the composites was determined. The influence of the material and rake angle of individual tools on the cutting force components was also determined. Measurements of the main (tangential) cutting force showed that, using large rake angles for uncoated carbide tools, one could obtain maximum force values that were similar to those obtained with polycrystalline diamond tools with a small rake angle. The results of the analysis of the tangential component of cutting resistance showed that, regardless of the rake angle, the values range from 140 N to 180 N. An analysis of the feed component of cutting resistance showed that the maximum values of this force ranged from 46 N to 133 N. The results showed that the highest values of the feed component of cutting resistance occurred during the machining of polymer composites with carbon fibers and that they were most affected by feed per tooth. It was also shown that the force models determined during milling with diamond insert tools had the highest coefficient of determination in the range of 0.90–0.99. The cutting resistance analysis showed that the values tested are in the range of 3.8 N/mm² to 15.5 N/mm². Full article

We investigated the morphological patterns, crystalline structures and their thermal stability in solidified Au–Ge nanoparticles ranging in size from 10 to 500 nm. Liquid Au–Ge alloy nanoparticles with hypoeutectic composition were rapidly cooled from a temperature of 500 °C in a TEM and characterized using advanced TEM techniques. We demonstrated that Au–Ge nanoparticles 10–80 nm in size predominantly solidified into a Janus-like morphology with nearly pure single-crystalline hcp Au and diamond cubic Ge domains. These particles remained stable up to the eutectic temperature, indicating that Ge doping and particle size play key roles in stabilizing the hcp Au phase. In turn, larger nanoparticles exhibited a metastable core–shell morphology with polycrystalline Ge shell and hcp Au-Ge alloy core under solidification. It was shown that the mentioned morphology and crystalline structure evolved into the equilibrium Janus morphology with fcc Au and diamond Ge domains at temperatures above ≈160 °C. Full article

Microwave Plasma Chemical Vapor Deposition (MPCVD) plays a crucial role in the growth of high-quality diamonds. However, during the MPCVD process, residues such as polycrystalline diamond, and graphite often adhere to the high-temperature growth substrate surfaces, potentially degrading diamond growth quality. To effectively remove these contaminants and improve the quality of diamond growth, this study employed an 800 kHz femtosecond laser to clean growth substrates with residual deposits. We assessed the effects of multiple cleaning cycles on residue removal from the Foundation Trench Region (FTR) and Inwall Region (IR) and on substrate quality. The results indicate that multiple scans at a laser power of 2.38 W, a repetition rate of 800 kHz, a scanning speed of 1800 mm/s, and a scan spacing of 10 μm significantly removed residues, reduced substrate surface roughness, and restored substrate cleanliness. This approach enhances the quality and efficiency of diamond growth via MPCVD. The application of high-repetition-rate femtosecond laser cleaning techniques for growth substrates significantly improves the quality of regenerated diamond films, providing crucial support for the preparation of high-quality diamond materials. Full article

Polycrystalline diamond (PCD), which is widely used to manufacture cutting tools due to its extreme hardness, in most cases requires grinding for machining. The cooling lubricant selected for PCD grinding largely affects the frictional conditions and the thermo-mechanical load collective between the diamond grinding wheel and the PCD. As a consequence of this, the material removal and grinding wheel wear mechanisms during grinding PCD depend on the cooling lubricant used. In this study, experimental and numerical investigations were taken into account, demonstrating that using a water-based cooling lubricant during PCD grinding predominantly leads to a mechanical load on workpiece and grinding wheel rather than thermal loads. These original findings can be used to complement existing explanatory models of the PCD grinding process valid for grinding with oil as a cooling lubricant. The aim of this work is to contribute a novel extension to the existing material removal and grinding wheel wear models to enable them for the grinding process with a water-based cooling lubricant. The knowledge obtained from this work is intended to serve as a basis for future industrial process design. Full article

In recent years, polycrystalline diamond compact (PDC) drill bits have seen significant advancements. They have replaced over 90% of the workload traditionally handled by roller cone bits and have become the predominant choice in energy drilling due to their superior efficiency and durability. However, PDC drill bits are susceptible to adhesion of rock cuttings during drilling in muddy formations, leading to mud accumulation on the bit surface. This phenomenon can cause drill bit failure and may contribute to downhole complications, including tool failure and borehole instability. The adhesion issue between PDC drill bits and mud rock cuttings underground is primarily influenced by the normal adhesion force between the drill bit surface and the mud rock cuttings. Therefore, biological non-smooth surface technology is applied to the prevention and control of drill bit balling. It is an optimal selection of biomimetic non-smooth surface structures with reduced adhesion and detachment properties. A non-smooth surface model for the PDC drill bit body is established through the analysis of the morphological characteristics of natural biological non-smooth surfaces. An experimental platform is designed and manufactured to evaluate the adhesion performance of non-smooth surface specimens. Indoor experiments are conducted to test the normal adhesion force of non-smooth surface specimens under varying morphologies, sizes, and contact times with clay. Finally, the anti-adhesion performance of the non-smooth surface unit structures is then analyzed. The normal adhesion force with a contact time of 12 h is as follows: 340 Pa of big square raised, 250 Pa of middle square raised, 190 Pa of small square raised, 315 Pa of big circular groove, 280 Pa of middle circular groove, 200 Pa of small circular groove, 225 Pa of big dot pit, 205 Pa of middle dot pit, and 130 Pa of small dot pit. Compared with the normal adhesion force of 550 Pa for smooth surface specimens with a contact time of 12 h, the anti-adhesion properties of the three non-smooth surface unit structure specimens designed in this paper were verified. We analyzed the anti-adhesion performance of non-smooth surface unit structures. At the critical contact time when the adhesion force tends to stabilize, the adhesion forces of different specimens are as follows: 330 Pa of big square raised, 237.5 Pa of middle square raised, 175 Pa of small square raised, 290 Pa of big circular groove, 250 Pa of middle circular groove, 160 Pa of small circular groove, 210 Pa of big dot pit, 185 Pa of middle dot pit, and 115 Pa of small dot pit. The results indicate that the anti-adhesion effect of small dot pit structures is the most effective, while the anti-adhesion effect of large square convex structures is the least effective. As the size of the unit structure decreases, it becomes more similar to the surface size of the organism. Additionally, a shorter contact time with clay leads to a better anti-adhesion effect. These findings provide new insights and research directions for the effective prevention and control of mud wrapping on PDC drill bits. Full article

Flow injection analysis (FIA) is widely used in drug screening, neurotransmitter detection, and water analysis. In this study, we investigated the electrochemical sensing performance of glassy graphene electrodes derived from pyrolyzed positive photoresist films (PPFs) via rapid thermal annealing (RTA) on SiO₂/Si and polycrystalline diamond (PCD). Glassy graphene films fabricated at 800, 900, and 950 °C were characterized using Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) to assess their structural and morphological properties. Electrochemical characterization in phosphate-buffered saline (PBS, pH 7.4) revealed that annealing temperature and substrate type influence the potential window and double-layer capacitance. The voltammetric response of glassy graphene electrodes was further evaluated using the surface-insensitive [Ru(NH₃)₆]^3+/2+ redox marker, the surface-sensitive [Fe(CN)₆]^3−/4− redox couple, and adrenaline, demonstrating that electron transfer efficiency is governed by annealing temperature and substrate-induced microstructural changes. FIA with amperometric detection showed a linear electrochemical response to adrenaline in the 3–300 µM range, achieving a low detection limit of 1.05 µM and a high sensitivity of 1.02 µA cm⁻²/µM. These findings highlight the potential of glassy graphene as a cost-effective alternative for advanced electrochemical sensors, particularly in biomolecule detection and analytical applications. Full article

The Chang’e project has completed a sampling mission of the shallow lunar soil layer; however, the exploration of the deep lunar rock layer remains unaddressed. To further investigate the feasibility of deep lunar rock drilling and identify the factors affecting the rate of penetration (ROP) and power in low-temperature, H₂O less environment, a model was developed. This study utilized the Box–Behnken method to design a response surface experiment, where the number of polycrystalline diamond compact (PDC) cutters, the backward inclination angle, the chip removal conditions, and the temperature were considered as the key influencing factors. A response surface model for ROP and power was established. The results indicated that the number of PDC cutters, the backward inclination angle, the chip removal conditions, and the temperature significantly affected both ROP and power, with the interaction between the temperature and the backward inclination angle having a particularly strong impact on the ROP. The regression model demonstrated high predictive accuracy for both ROP and power, with goodness of fit (R²) values of 0.95 and 0.96, respectively. The optimal combination of the backward inclination angle, number of PDC cutters, temperature, and chip removal conditions, derived from the response surface experiment, was 25°, four, −15 °C, and 1, respectively, which resulted in high drilling efficiency and low power consumption. This study offers new insights for the design of deep lunar drilling experiments, as well as support for the future optimization of drilling tools. Full article

Focused Ion Beam (FIB) has been used to create single α-β colony micro-pillars from a polycrystalline commercial Ti-6Al-4V (Ti-64) sample. Each pillar was selected to have either a single alpha phase, a single beta phase, or two α lamella separated by a thin β phase filet. Then, utilizing a diamond flat tip as a compression platen, uniaxial micro-compression tests were performed on the single crystal α and β pillars as well as a tri-crystal α/β/α pillar using a nano-indenter. Then, utilizing a diamond flat tip as a compression platen, uniaxial micro-compression tests were performed on the single crystal alpha and beta pillars as well as a tri-crystal α/β/α pillar using a nano-indenter. Through the use of Electron Back Scattering Diffraction (EBSD) to choose the crystal orientation along the micro-pillar, three distinct unique slip systems have been selectively triggered by maximizing the Schmid factor for each system. The potential to localize a single crystal volume that can be characterized after deformation is one benefit of the micro-compression approach over traditional mechanical testing. The sample strengths compare well with published data. The mechanical properties of the α-β colonies and the single α and β phases have been compared in order to elucidate the role of the α/β interfaces in determining the critical resolved shear stress. Full article

Reducing the auxiliary drilling time and improving the drilling efficiency are not only important technical means to enhance the development and deep exploration of oil and gas reserves, but also have significant implications for ensuring energy security. Bottom hole self-renewal drill bit technology is a new technology that does not require the retrieval of drills from the well bottom, instead directly updating worn drill bits in place. Through the self-renewing structure of the drill bit, the sustainability of the drill bit can be increased. Conducting research on this technology is expected to overcome the technical issues related to the short useable life of drill bits, thus promoting single-trip drilling technology. This article summarizes the scientific progress made by researchers in self-renewal Polycrystalline Diamond Composite (PDC) drill bit technology; for example, the American National Oilwell Varco (NOV) company has developed a mobile self-renewal cone bit technology and introduced the structural characteristics and working principles of three types of rotating self-renewal drill bits: rack-driven, worm-driven, and ratchet-driven. This study compares and analyzes the advantages and disadvantages of these three rotary types of PDC drill bits, providing a detailed introduction to the working principles and modes of the triggering, transmission, limit and locking, and renewal structure devices of the drill bit. Relevant suggestions are proposed for the development of bottom hole self-renewal PDC drill bit technology; namely, strengthening research efforts relating to the intelligent judgment and recognition of cutting tooth wear of the drill bit, as well as the integration of multiple technologies. The sustainability of these novel bits can provide technical support for the development of single-trip drilling technology for deep formations, improve the service life of bits in deep formations that are difficult to drill, and contribute to the efficient development of deep-sea energy resources worldwide. Full article

In high-temperature geothermal wells, the formation usually has extremely high abrasiveness, hardness, and temperature, which pose severe challenges to drilling tools. Among them, the interaction between the cutter of the drill bit and the rock is the key factor determining the rock-breaking efficiency of PDC (Polycrystalline Diamond Composite) drill bits. To further explore the rock-breaking mechanism of cutters on granite, this study adopts a combination of experimental and simulation methods to conduct systematic research. The results indicate that the specific crushing work increases and then decreases with rising temperature, reaching a minimum of 0.388 J/mm³ at 200 °C. In the temperature range of 300 °C to 500 °C, the specific crushing work is 15% lower than at room temperature. The specific crushing work during instant cooling is 12–25% lower than that during self-cooling, with instant cooling showing higher rock-breaking efficiency. As the rake angle increases, the specific crushing work initially decreases and then increases. The smallest specific crushing work, 0.383 J/mm³, occurs at a rake angle of 10°, where the number of debris and particle size are maximized. With deeper cutting depths, the specific crushing work gradually decreases, resulting in more debris, larger particle sizes, and higher cutter surface temperatures. These findings clarify the variation laws of rock load, cutting tooth distribution, and rock fragmentation state when the PDC bit breaks rocks. A rake angle of 10° can be used as the selection of cutting tooth inclination angle for PDC bit design, providing a theoretical basis for the design and application of PDC bits in high-temperature geothermal drilling and holding significant guiding importance. Considering that increasing the depth of penetration can cause uneven wear of the cutter, the drilling parameters can be controlled under certain conditions to achieve a penetration depth of 2 mm, thereby improving the rock-breaking efficiency and working life of the PDC bit. Full article

A review of binder phases used for sintering diamond powders under high pressure and high temperature conditions along with an outline of the properties of polycrystalline diamonds or composite materials intended for cutting tools, wire drawing dies, and drilling rocks are presented. The interaction of diamond with metals from group VIII of the periodic table, carbon-forming metals, carbides, MAX phases and with silicides, borides, and alkali carbonates is presented. The interaction of the bonding phases with diamond was determined. The influences of sintering process parameters, amounts, and methods of introducing of these phases on the basic mechanical properties and thermal resistance of diamond materials are analyzed. The investigated material properties are compared with the properties of commercial PCD with a cobalt and the SiC binder phase. Full article

The flow occurring at the bottom of a polycrystalline diamond compact (PDC) drill bit involves a complex process made up of drilling fluid and the drilled rock cuttings. A thorough understanding of the bottom-hole flow conditions is essential for accurately evaluating and optimizing the hydraulic structure design of the PDC drill bit. Based on a comprehensive understanding of the hydraulic structure and fluid flow characteristics of PDC drill bits, this study integrates computational fluid dynamics (CFD) with rock-breaking simulation methods to refine and enhance the numerical simulation approach for the liquid–solid two-phase flow field of PDC drill bits. This study further conducts a comparative analysis of simulation results between single-phase and liquid–solid two-phase flows, highlighting the influence of rock cuttings on flow dynamics. The results reveal substantial differences in flow behavior between single-phase and two-phase conditions, with rock cuttings altering the velocity distribution, flow patterns, and hydraulic performance near the bottom-hole region of the drill bit. The two-phase flow simulation results demonstrate higher accuracy and provide a more detailed depiction of the bottom-hole flow, facilitating the identification of previously unrecognized issues in the hydraulic structure design. These findings advance the methodology for multiphase flow simulation in PDC drill bit studies, providing significant academic and engineering value by offering actionable insights for optimizing hydraulic structures and extending bit life. Full article

This study investigates the intricate relationship between bit rock interactions and drilling parameters for multiple-diameter hole drilling scenarios. Two sets of experiments were conducted in the Drilling Technology Laboratory at Memorial University of Newfoundland (DTL-MUN) using a fully instrumented Large-scale laboratory Drilling Simulator (LDS). The study contained two critical stages. Pre-coring operations using various diameter coring bits were completed to ensure thorough analysis. Next, drilling using a 5-cutter Polycrystalline Diamond Compact (PDC) bit with a larger diameter than all pre-cored holes, at constant Weight on Bit (WOB) and Revolution per Minute (RPM), was performed. The type of rock used in the experiments is a high-strength gabbro formation. Results indicate that pre-cored holes exhibited higher Rates of Penetration (ROP) than un-pre-cored holes, reflecting improved drilling performance and higher torque due to reduced bit–rock interaction area. A distinct relationship was observed between bit–rock interactions, torque, ROP, Mechanical Specific Energy (MSE), and applied WOB in multi-diameter drilling. ROP decreased as the pilot hole diameter decreased due to increased bit–rock interaction. The recorded data of WOB and the torque responses showed a decrease in amplitude as the bit–rock interface area increased, suggesting a positive interaction between drilling efficiency and downhole conditions. The modified Maurer model found a correlation between increased pilot hole diameter and decreased effective rock strength. These results highlight the significance of conducting a thorough drilling parameter analysis and the need for additional study to clarify the underlying mechanisms influencing drilling performance in multi-diameter hole drilling scenarios. Full article

As the extraction of oil and gas progresses into deeper and ultra-deep geological formations, the enhancement of rock-breaking efficiency in drill bits has emerged as a critical factor in ensuring energy security. Among the various techniques employed, vibratory percussion drilling technology is widely recognized for its ability to improve both the efficiency and speed of penetrating hard rock formations. This study examined the effects of varying loading conditions on the characteristics of rock fracture and damage, maintaining a constant cutting speed and lead angle. By designing a small polycrystalline diamond compact (PDC) drill bit and incorporating simulation results, the research sought to analyze the influence of axial impact components on the efficiency of breaking dolomite samples, as well as the effects of impact frequency and amplitude on drilling pressure and rock-breaking energy. The findings revealed that an increase in the axial impact amplitude significantly enhanced rock-breaking efficiency, elevated von Mises stress, and increased principal compressive stress. An increase in impact frequency effectively reduced the overall stress and frictional work. These results underscored that the stress analysis revealed that the peak stress increased at lower impact amplitudes, with notable changes occurring at an amplitude of 1.5, leading to a 100% increase in Mises peak stress compared with an amplitude of 1.0. Axial impact drilling promoted deep crack formation and the development of a tensile damage zone beneath the cutter, indicating its effective rock-breaking capabilities. Axial impact drilling significantly reduced the threshold drilling pressure compared with conventional rotation, with an impact amplitude of 0.3 mm decreasing the static load by 44.1%. Additionally, increasing the axial impact amplitude enhanced the rate of penetration (ROP) while maintaining a constant static load, resulting in remarkable efficiency improvements. The results of the study are expected to provide theoretical guidance for the mechanism of impact rock breaking and the design of impact rock-breaking tool parameters. Full article