Diamond Composites Research Articles

Friction and wear characteristics of synthetic diamond and graphene-filled polyether ether ketone composites

Modifying tribo films using filler particles is a significant area of research in developing polymer-based tribo components to minimize material loss during the sliding process. This study focused on altering the wear characteristics of a polyetheretherketone (PEEK)/graphene high-performance polymer composite to strengthen the tribo film by adding synthetic diamond particles. The hot-pressed PEEK composite reinforced by graphene and diamond particles increased the hardness and thermal stability of the composite. Compared with pure PEEK, composites containing 1% graphene and 1% diamond particles showed an increment of 25% and 23% in hardness and thermal stability, respectively. Fourier-transform infrared spectroscopy and X-ray diffraction analysis verified the compatibility and intactness of the fillers in the PEEK matrix. The tribo properties of PEEK composites were characterized by a pin-on-disc tribometer on a counter steel surface. A PEEK composite containing 0.75 wt% graphene and 0.5 wt% diamond particles exhibited the lowest friction of 0.17 at a pressure of 1.5 MPa. The specific wear rate was low (1.78 × 10−6 mm3/Nm) for the composite containing 1 wt% graphene and 1 wt% diamond particles at a pressure of 1.5 MPa. Varying synthetic diamond and graphene filler concentrations in the PEEK matrix change the wear process by modifying the tribo film characteristics, revealing the lowest friction and wear rate. X-ray photoelectron and Raman spectroscopy show that the polymer film was transferred to the steel countersurface, and the tribo-chemical products of the tribo film contribute to a stable tribo film. The ferric oxide film and the tribo film improve the composite’s self-lubricating properties and load-bearing ability. Hence, the composite containing 0.75% of graphene and 0.5% of a synthetic diamond can be employed in the sliding bearing application of continuous conveyors used in mass production systems.

Diamond composites with Al-Co binder: Synthesis, structure, wear resistance

Wear-resistant diamond composites without a tungsten carbide substrate were obtained by sintering mixtures of micron and submicron diamonds at 7–8 GPa, 1550–1700 °C. Cobalt and aluminum powders were used as sintering activators in a proportion that ensures the formation of microstructure with binding phases in the form of intermetallic AlCo and carbide AlCo3C.The influence of the morphology and sizes of diamond particles on the microstructure and performance characteristics of composites is considered. The possibility of hard alloy turning with new composites from homogeneous mixtures in the quasi-ductile mode is demonstrated. The wear resistance of experimental samples with optimized initial composition and shape of diamond particles significantly exceeds the characteristics of high-quality commercial composites used in drill bits.

Influence of diamond parameters on microstructure and properties of copper-based diamond composites manufactured by Fused Deposition Modeling and Sintering (FDMS)

As an additive manufacturing technology, Fused Deposition Modeling and Sintering (FDMS) technology can give diamond tools some creative structures to be applied in more fields. To explore the influence of diamond parameters on diamond tools manufactured by FDMS, copper-tin-diamond composite samples with different diamond concentrations and particle size were prepared by FDMS technology in this paper. During the study, the morphological characteristics of diamond particles inside the samples during the debinding and sintering process are summarized and the influence of diamond parameters on the mechanical properties and structure of the samples was further explored. These influence laws were also verified by cutting experiments. The results show that most diamond particles are in an incomplete coating state because of the volatilization of the binder. Meanwhile, a higher concentration of diamond will lead to more pores and cavities in the samples; and the cavities can be connected to form a large area of cavity zone by the print layer, thereby resulting in a serious loss in the performance of the samples. On the other hand, a small diamond particle size can lead to agglomeration of particles. Subsequently, this will result in void generation and regional weakening of the holding ability. However, agglomeration and some pores or cavities will increase the wear of the matrix, expose more diamond particles, and finally improve the cutting efficiency of the dicing blades when cutting sapphire crystal. Excessive wear may reduce the life of the diamond tool, but improved of sharpness can be better applied in the field of precision machining.

Mechanical property of all-composite diamond honeycomb sandwich structure based on interlocking technology: Experimental tests and numerical analysis

In this study, a three-rib intersecting composite diamond honeycomb structure is fabricated by interlocking technology. The mechanical properties of the composite interlocked diamond honeycomb (CIDH) and corresponding sandwich structure (CIDHSS) are experimentally tested. The stiffness, strength, and failure characteristics of CIDH and CIDHSS are analyzed. The results show that CIDH has better mechanical properties than the interlocked Kagome and square honeycombs. The edge effect limits the edge compressive strength and stiffness of CIDH. Debonding is the main failure mode that limits both bending and compressive strength of CIDHSS. The reinforced plate added to the edge effectively improves the anti-debonding ability.

Reactive spark plasma sintering of SiC-TiC-diamond composites

SiC-TiC-diamond composites were fabricated via spark plasma sintering at hold temperatures of 1600 °C, 1625 °C, and 1650 °C from a powder blend containing by weight 30 % Si, 30 % Ti, and either 40 % uncoated or TiC-coated diamond. Due to the sintering conditions, sp3-diamond decomposed into thermodynamically favorable sp2‑carbon, reacting with Si and Ti to form SiC and TiC at T ≥ 1600 °C. As the hold temperature increased, the composite density reduced due to excess graphite formation for the uncoated diamond composites. However, at too low of a temperature the porosity fraction increased in the SiC-TiC matrix for the TiC-coated diamond composites. Overall, the results revealed that composites with ~97 % theoretical density and minimal (up to 5 vol%) graphite can be achieved by sintering Si-Ti-uncoated diamond at 1600 °C and Si-Ti-TiC-coated diamond at 1625 °C. X-ray diffraction, electron and x-ray microscopies with imaging analyses were carried out to quantify the volume fractions of each composite phase and used to explain the composite densification behavior. Conventional and energy filtered transmission electron microscopy, in addition to electron energy loss spectroscopy, were conducted to understand the nature of diamond graphitization with respect to the nucleation and growth of SiC, TiC, and nanoscale graphite.

Quantitative investigation of thermal evolution and graphitisation of diamond abrasives in powder bed fusion-laser beam of metal-matrix diamond composites

ABSTRACT Preventing the thermal damage of diamond abrasives is the major challenge of diamond composites in the field of super-hard tools by laser additive manufacturing. In the presented work, we established a quantitative framework to accurately evaluate the thermal damage behaviour and the relevant microstructure-performance characteristics, by using CuSn10-diamond composite by powder bed fusion-laser beam (PBF-LB). By simulating the thermal history of diamond in the molten pool and microstructure characterisation, the critical temperature of 1491.6°C of diamond graphitisation was obtained. Below the critical temperature, the composite with no diamond-graphitisation exhibited abrasive wear and wear loss rate below 0.01%. The increasing temperature led to the aggravation of graphitisation, which ID: IG value changed from 2.00 to 0.57 with the temperature increasing from 1491.6°C to 1896.1°C, resulting in wear mechanism changing from adhesive wear to three-body abrasion, with the wear loss rate from 0.01% to 0.73%. Integrating the results of simulation, microstructures and wear properties, the graphitisation threshold of diamond in PBF-LB was revealed and the quantitative relationship of ‘PBF-LB parameters - Temperature - Graphitisation degree - Wear resistance’ of the metal-matrix diamond composites was established.

Influence of CrB2 additive on the morphology, structure, microhardness and fracture resistance of diamond composites based on WC‒Co matrix

In the paper, structure and properties of novel diamond composite with enhanced properties were presented and discussed. The samples were prepared using the method of cold pressing followed by the originally developed two-stage vacuum hot pressing under electric current activation. It was demonstrated that addition of different amounts of chromium diboride to the WC–6 wt.%Co composite had significant effect on its microstructure, phase composition and, hence, mechanical characteristics. It was found that percentage 4 wt.% of CrB2 provided the most advantageous characteristics. In the second stage of researches, this composition was used as a matrix for the diamond reinforcement. The obtained results of analysis suggested that enhancement of the composite could be attributed to the dispersed strengthening mechanism and structure modification. In particular, important role played reduction of the average grain size of the carbide phase from 5.6 to 3.4 μm, disappearance of pores at the Co binding phase, formation of inhibitor phase clusters at the interphase boundaries, and the specific pattern of phases present in the composite. Chromium diboride contributed also to the formation of dense and strong interface between diamond grits and refractory matrix. Advantageous distribution of residual stresses around the diamond grits appeared in the sintered samples with CrB2, providing additional fixation of the diamond reinforcement in the matrix. It was also demonstrated that further increase of CrB2 content above 4 wt.% in the WC–6 wt.%Co composite material lead to a deterioration in its mechanical properties, which could be attributed to further, disadvantageous changes in the structure, especially in grain size and phase composition.

Research on controllable ozone oxidation on diamond surface

In recent years, there have been more and more researches on the surface modification of diamonds, however, the exact types and quantities of oxygen-related species on diamond surfaces and the method to control the condition parameters to obtain as many oxygen-containing groups as possible have been rarely studied so far. Therefore, in this work, we focused on these questions. And we find out that ozone oxidation would not affect the overall crystal structure and morphology of diamonds. Besides, changing oxidation time and ozone concentration would significantly influence the density of hydroxyl groups, which is manifested as a change of oxygen content. In order to make the hydroxyl density on diamond surface reach a high level (3.12 × 1014 units/cm2), so that diamonds can be better combined with the resin matrix, the ozone oxidation time should be 15 min, and the ozone concentration should be 115 g•m−3. And under these conditions, the thermal conductivity of diamond and polysiloxane composites can reach 8.02 W/mK.

Prospects for the Use of Fluorinated Nanodiamonds in the Synthesis of Superhard Composites

The paper considers the possibilities of the practical use of nanoscale diamonds with a fluorine-functionalized surface for the synthesis of diamond composites under high pressures and temperatures. Optimal compositions of the initial mixtures and parameters of thermobaric treatment are established. It is shown that composites obtained by sintering homogeneous mixtures of fluorinated microdiamonds and nanodiamonds with the addition of aluminum and cobalt have an increased level of heat resistance and wear resistance which significantly exceeds the level of commercial samples.

Selective Deposition of Mo2C-Containing Coatings on {100} Facets of Synthetic Diamond Crystals.

An efficient way to improve the properties of metal–diamond composites (mechanical strength, wear resistance, thermal conductivity) is the preliminary modification of the diamond surface to improve its wettability by the metal matrix. In the present work, Mo2C-containing coatings were deposited on the diamond crystals under different conditions: hot pressing (atmosphere of argon), spark plasma sintering (forevacuum), and annealing in air. The influence of the sintering parameters on the morphology and phase composition of the coatings deposited on diamond was studied. Mo2C-containing coatings were selectively deposited on the facets of synthetic diamond microcrystals by annealing of the latter with a molybdenum powder. Experiments were carried out to deposit coatings under different conditions: during hot pressing (argon atmosphere), spark plasma sintering (forevacuum), and annealing in air. The process parameters were the temperature, holding time, and concentration of molybdenum in the initial mixture. Experiments with a pre-oxidized molybdenum powder were also conducted. The coated diamond crystals were investigated by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The deposition was enabled by the gas phase transport of molybdenum dioxide, MoO2, contained in the starting powder. The following sequence of the coating formation stages was proposed. First, MoO2 sublimes and is adsorbed mainly on the {100} facets of diamond. Then, it is reduced to metallic molybdenum by carbon of the diamond, which further reacts with carbon to form the Mo2C carbide phase. These processes occurred during treatment of the mixtures in the hot press and the spark plasma sintering facility. When the mixture was annealed in air, no selective deposition was observed. During annealing, MoO3 particles adhered to the diamond surface.

Diamond Composites Produced from Fluorinated Mixtures of Micron-Sized and Nanodiamonds by Metal Infiltration.

Improving the operating performance of superhard composites is an important and urgent task, due to a continuing industrial need. In this work, diamond composites with high wear resistance were obtained by sintering fluorinated mixtures of micron-sized diamonds with nanodiamonds at high pressures and temperatures (7–8 GPa, 1550–1700 °C). Aluminum and cobalt powders were added to the diamond mixture to activate the process. The external infiltration of nickel into the diamond layer was carried out additionally during the sintering process, and the effects of nickel infiltration on the structure and properties of composites were studied. The metal melt ensured the mass transfer of carbon within a volume, and the formation of a strong diamond framework. The composition of the additives was selected in such a way that the binding phase became ultimately composed of the intermetallic AlNixCo1−x(x ≤ 1). The Young’s modulus of composites synthesized in this way had a value of 850 GPa, and their wear resistance when turning white granite was more than twice as high as that of premium commercial PDC. The obtained results thus demonstrate that by using nickel to increase melt infiltration into diamond-based composites, the mechanical properties of Al/Co/fluorinated diamond compositions, studied previously, can be further improved.

Modeling and experimental research on temperature field of full-sized PDC bits in rock drilling and coring

To study the effect of drilling rig working parameters and rock type on the temperature of the polycrystalline diamond composite (PDC) bit, an analytical temperature calculation model was established, and the correctness of the analytical model was verified by numerical simulation analysis. Combined with an infrared thermal imager, the temperature of PDC cutting teeth under different parameter combinations was qualitatively analyzed, and the sensitivity of cutting teeth temperature to different parameters was discussed through an orthogonal test. The research results show that increasing the rotational speed and rate of penetration (ROP) value causes more severe shearing and friction of the bit, thereby increasing the temperature of the cutting teeth. The experimental results are consistent with the simulation results. Under the same working parameters, the maximum temperature of the bit when drilling granite is about 1.5 times that of curbs and 2 times that of artificial rocks. Finally, the orthogonal test analysis found that the cutting teeth temperature has a high sensitivity to rock type and ROP value, with a weight of 48% and 32.9%, respectively; also, the index has a general sensitivity to the rotation speed, with a weight of 19.1%. The research results provide a certain reference value for the reasonable selection of the working parameters of the drilling rig.

Fabrication and application of CNT fiber-ultra-fine diamond composites via electrophoretic deposition and instantaneous Joule-heating method

One-dimensional carbon nanotube (CNT) fibers combined with three-dimensional ultra-fine diamond have a synergistic effect that can be used in a variety of applications. The current challenge is how to combine the two materials quickly and efficiently. To actualize the combination of the two materials, a two-step method is adopted in this study. The electrophoretic deposition method, which allows ultra-fine diamond particles to adhere uniformly and controllably to the surface of carbon nanotube fibers. The instantaneous Joule-heating method can realize the instantaneous high-temperature recombination of diamond and CNT fibers. CNT fibers' flexibility and thermal conductivity are combined with ultra-fine diamond's high hardness in this composite. A polishing tool was made by knitting ultra-fine diamond/CNT fiber threads on non-woven fabric and used to dry polish potassium dihydrogen phosphate (KDP) crystals. CNT fibers were examined for wear, surface morphology, and KDP surface roughness before and after processing. The results reveal that the composite material-prepared tool has greater wear resistance and machining efficiency.

Impact of Ce2O3 on microstructure and properties of matrix-body for PDC drill bits synthesized via pressureless melt infiltration

The materials of matrix-body polycrystalline diamond composite (PDC) bits were fabricated through pressureless melt infiltration method at 1200 °C for 1 h within vacuum furnace using molten CuNi metallic binder, Ni and WC powders (including cast WC, spherical WC, and fine WC). Various weight ratios of Ce2O3/(WC + Ni + CuNi) ranging from 0 to 0.01 were added to matrix-body materials. The influence of Ce2O3 on the microstructure, phase formation, phase transformations, and related mechanical properties of matrix-body materials was thoroughly investigated. The results show that experimental temperature led to the decomposition of WC and partial dissolution of W and C in CuNi binder alloys. In matrix-body materials with no Ce2O3 addition, only new W2C phase was formed. With further increase in Ce2O3/(WC + Ni + CuNi) ratios, spherical WC was dispersed into smaller WC particles. Meanwhile, new phases (namely Ni2W4C, C, and W2C) were found. The material exhibited an optimal hardness (HRA = 93.7) and transverse rupture strength (1846.8 MPa) when Ce2O3/(WC + Ni + CuNi) ratio was 0.006. However, impact toughness was slightly decreased, while the highest value of 6.45 J cm−2 was measured for the sample with Ce2O3/(WC + Ni + CuNi) ratio of 0.01.

Properties of Cutting Tool Composite Material Diamond–(Fe–Ni–Cu–Sn) Reinforced with Nano-VN

The study is devoted to structure and mechanical properties of a diamond composite used for manufacturing of cutting tools applied in a wide range of technological fields. The sample tools were fabricated by cold-pressing technology followed by hot-pressing in vacuum of the 51Fe–32Cu–9Ni–8Sn matrix mixture with diamond bits, both in absence and presence of nano-VN additives. It was demonstrated that without VN addition, the diamond–matrix interface contained voids and discontinuities. Nanodispersed VN added to the matrix resulted in the formation of a more fine-grained structure consisting of solid solutions composed of iron, copper, nickel, vanadium and tin in different ratios and the formation of a tight diamond–matrix zone with no visible voids, discontinuities and other defects. Optimal concentrations of VN in the CDM matrix were found achieving the maximum values of nanohardness H = 7.8 GPa, elastic modulus E = 213 GPa, resistance to elastic deformation expressed by ratio H/E = 0.0366, plastic deformation resistance H3/E2 = 10.46 MPa, ultimate flexural strength Rbm = 1110 MPa, and compressive strength Rcm = 1410 MPa. As-prepared Fe–Cu–Ni–Sn–VN composites with enhanced physical and mechanical properties are suitable for cutting tools of increased durability and improved performance.

Effect of surfactants on vitrified bond diamond composites prepared by sol-gel and dispersibility of diamond

Vitrified ultrafine diamond grinding wheels are ideal for machining next-generation semiconductor power device material, such as SiC etc. However, a crucial problem limiting the application of ultrafine diamond originates from the dispersion of aggregates in vitrified bond. In this study, in can be confirmed that the preparation of uniformly dispersed diamond/vitrified bond composites using sol-gel technique is feasible. Surfactants with various types and additions interactively promote the dispersion of diamond, which make both the bending strength and diamond dispersion of the composites are suitable for precision grinding. The results are valuable for the preparation of vitrified grinding wheels with ultrafine diamond for precision machining of semiconductor.

Efficient electromagnetic micropunching technology for producing well-ordered, high-density micropits

ABSTRACT Micropits are favorable for interfacial lubrication and cell culturing. This study developed an AC electromagnetic-driven high-speed micropunching mechanism capable of rapidly fabricating a large-numbered array of well-ordered micropits. The designed mechanism converts 60-Hz AC into 120-Hz electromagnetic force, which in turn drives a punching-shaft to complete a high-speed punching movement at 120-Hz. The micropunching mechanism is installed on a desktop gantry framework to create a stable, high-speed CNC micropunching system. Combining an eddy current sensor with an oscilloscope determines optimal spring stiffness for the system. A micropunching experiment is performed using a micropunching tool comprised of electrically conductive polycrystalline composite diamond (ECPCD) and an annealed aluminum alloy workpiece. The results revealed that a 120-Hz punching-frequency, a spring stiffness of 2.7 N/mm, and a workpiece moving speed of 2160 mm/min generate micropits with a high-integrity profile. It takes only 3.4 seconds to complete 400 high-integrity, well-organized micropits, with a depth of 23.0–23.3 μm that are burr-free and almost chipless, indicating the proposed high-speed electromagnetic micropunching technology is highly precise and efficient while also being energy-saving.

Influence of the powder metallurgy route on the mechanical properties of Cu–Cr–diamond composites

Metal-bonded grinding tools are commonly based on copper as bond material and possess low porosity. The powder metallurgic fabrication and the applied process parameters have a high influence on the mechanical properties of these grinding layers. In this study, Cu–diamond composites are fabricated through Field Assisted Sintering Technology with a variation of holding time, temperature, pressure, and chromium powder particle size. The addition of chromium to these composites can ensure a higher adhesion of the diamonds through carbide formation within the interface of the diamonds and the copper bonding matrix. The coating of diamond with chromium-carbide is mainly controlled by the chromium powder particle size, which leads to a higher critical bond strength with decreasing particle size. Maximum critical bond strength of 463 N/mm2 is reached using chromium with an average particle size of 10 µm. Increasing holding time decreases porosity and increases the critical bond strength of the composites. An increase of sintering temperature from 900 to 1040 °C leads to a decrease of porosity due to local melting of the copper. The interlocking of diamonds due to their high concentration of 50 vol% within the composites results in a relatively high porosity above 7%.Article HighlightsModelling of the influence of sintering temperature, sintering time and chromium particle size on the critical bond strengthAddition of chromium results in an in-situ formed carbide-layer when sintering above a temperature of 900 °CSmaller chromium particle sizes significant increase the mechanical stability of CuCr–diamond composites

Formation and Performance of Diamond (111)/Cu Interface from First-Principles Calculation

The interface formation and properties of composite materials are very important for the preparation of composite materials, and the bonding state and charge transfer between atoms in the interface have a particularly significant effect on the interface formation. In this work, the first-principles calculation method was used to study the adsorption behavior and molecular dynamics of copper atoms on the (111) surface of H-terminated diamond, and the adsorption energy and adhesion work of Cu atoms were calculated. The results show that the adsorption of copper atoms is not sensitive to the diamond (111) surface, the adsorption work is very small at the four high symmetry positions, and the adhesion work is the largest at the T4 position and is 0.6106 J/m2. Furthermore, according to the electron localization function (ELF) analysis, there is no compound formation between Cu and H atoms; only a small amount of charge transfer exists, which belongs to physical adsorption. The diamond–copper interface formed by the growth of adsorption sites is a metastable structure without energy stability. This work provides an important theoretical reference for understanding the formation mechanism of copper-based diamond composites.

Effect of nickel-plated graphite on microstructure and properties of matrix for Fe-based diamond tools

Nickel-plated graphite particles and unmodified graphite particles with different contents were added to the Fe-based diamond composites. The basic properties of those specimens were measured, including relative density, hardness, bending strength, abrasion ratio and holding force coefficient. And also, SEM, XRD and EDS were used to carry out microstructure characterization, phase analysis and element distribution of these specimens. The results show that nickel plating effectively improves the surface wettability of graphite particles. And it is determined that an element diffusion zone is formed on the transition interface between the nickel-plated graphite and the matrix materials, effectively enhancing the interfacial bonding strength. Also, the pores and cracks in the matrix generated by adding the graphite particles are reduced after nickel plating. Thus, the loss of basic properties of the specimens is restrained. But it is found the higher the graphite content is, the weaker the positive effect of nickel plating is. In addition, it is revealed that nickel plating plays a conducive part in the formation of graphite lubricants on the working surface, and nickel-plated graphites can slow down the thermal corrosion of the diamond particles inside the high-temperature sintered specimens.