Diamond Composites Research Articles

Pressureless sintering of Al/diamond materials using AlSi12 liquid phase

Aluminum/carbon composites have garnered significant attention due to their promising thermal and mechanical properties. However, traditional manufacturing processes typically involve high-pressure techniques to achieve part densification, rendering them costly and less practical for large-scale applications. In this study, aluminum-AlSi12/diamond composites were produced using a pressureless, liquid-phase sintering technique. By carefully optimizing the sintering parameters, the densification of the composites reached 86%. Notably, this was further improved to 94% when the diamond particles were coated with copper, demonstrating the benefits of surface modification in enhancing densification. This innovative approach highlights the potential of free sintering as an effective method to achieve high-density composites without resorting to expensive high-pressure methods.

Exposure behavior and drilling efficiency of basalt fiber composite impregnated diamond bits in hard granite

Impregnated diamond bits (IDBs) are widely used for drilling in hard formations. To improve the drilling efficiency and exposure behavior of IDBs in granite, three types of Cu-based basalt fiber (BF) composite IDBs were designed and prepared by using the medium-frequency induction hot-pressing and sintering method, in which 0 wt% BF and 25 vol% diamond were used in 0BF25D IDB, 1 wt% BF and 25 vol% diamond were used in 1BF25D IDB, 1 wt% BF and 20 vol% diamond were used in 1BF20D IDB. The drilling efficiency of each IDB was tested under different drilling pressures (WOB), and the exposure behavior of IDBs was investigated by scanning electron microscopy and ultra field microstructural characterization. Results show that drilling granite with grade 9 drillability, low drilling pressure can drill successfully with the addition of BF. The average rate of penetration (ROP) of 1BF20D IBD under 6 kN WOB was 4.78 m/h, which was improved by 60 %∼80 %, energy consumption decreased by 66 % for each meter, torque (TOB) decreased, and rotational speed (RPM) was more stable during the drilling process. The addition of BF and reasonable diamond concentration enhanced the holding power of the diamond which promoted the exposure of the diamond. The average exposed height of the diamond in 1BF20D IDB reached 121.2 μm with 22 %–29 % of the whole diamond.

Coherent Interface Migration Toughens Diamond

AbstractOvercoming the hardness‐toughness trade‐off in diamonds attracts much interest in physics, chemistry, materials science, and engineering. Recently synthesized nanotwinned diamond composite exhibits massive enhancement in fracture toughness without sacrificing its unprecedented Vickers hardness [Y. Yue et al., Nature 582, 370 (2020)]. Several mechanisms for the toughness enhancement are unveiled based on the edge‐cracked models while the mechanism from Vickers indentation has remained elusive. Here, the energy of nanotwinned diamonds, diamond polytypes, and diamond composites is systematically investigated from Vickers indentation simulation. The results show diamond structures dissipate energy by interface migration, accompanied by the phase transformation from diamond polytypes to the cubic diamond (3C diamond). By tuning the density and distribution of interfaces, the dissipated energy of the diamond is increased to more than twice that of a single‐crystal 3C diamond. This work complements the established mechanisms and provides a universal strategy for toughening diamonds and related materials.

Microstructure and Mechanical Properties of Diamond–Ceramic Composites Fabricated via Reactive Spark Plasma Sintering

In order to prepare diamond composites with excellent mechanical properties under non-extreme conditions, in this study, a diamond–ceramic composite was successfully prepared via reactive spark plasma sintering using a diamond–Ti–Si powder mixture as the raw material. The microstructures and mechanical properties of the diamond–ceramic composite sintered at different temperatures were studied. When the sintering temperature was 1500 °C, the diamond–ceramic composite exhibited a volume density of 3.65 g/cm3, whereas the bending strength and fracture toughness were high at 366 MPa and 6.17 MPa·m1/2, respectively. In addition, variable-temperature sintering activated the chemical reaction at a higher temperature, whereas lowering the temperature prevented excessive graphitisation, which is conducive to optimising the microstructure and mechanical properties of the composite.

Mass production and cutting performance of diamond coated cutting tools for machining titanium alloys

Diamond coated cutting tools are applied for machining difficult-to-machine materials of titanium alloys. However, the temperature field uniformity needs to be further improved for the mass production of diamond coated tools using the hot filament chemical vapor deposition (HFCVD) method. In this paper, the tools temperature distribution is simulated by the finite volume method (FVM) during the deposition of diamond coatings. An optimization method of deposition setting with fine filaments in dense arrangement (FFDA) is proposed, and the temperature distributions of the tools under the coarse filament in sparse arrangement (CFSA) and FFDA are simulated to systematically elucidate the effects of fine filament densification. Subsequently, the different hot filament arrangements are adopted to mass production experiment for deposition of micro/nano composite diamond (MCD/NCD) coatings on WC-6%Co cutting tools. In addition, the cutting experiments on titanium alloys are conducted using diamond coated tools, and the cutting performance of tools at different locations is evaluated. The results indicate that the FFDA method can improve the temperature field uniformity of mass-produced diamond coated cutting tools, and the cutting tools have better consistency in surface morphology, thickness, chemical composition, surface roughness and cutting performance.

Additive manufacturing of titanium–diamond parts: insights into the laser metal deposition process, powder rheology, mechanical properties and osteoblast cell viability

PurposeThe purpose of this study is therefore to detail an additive manufacturing process for printing TiD parts for implant applications. Titanium–diamond (TiD) is a new composite that provides biocompatible three-dimensional multimaterial structures. Thus, the authors report a powder-deposition and print optimization strategy to overcome the dual-functionality gap by printing bulk TiD parts. However, despite favorable customization outcomes, relatively few additive manufacturing (AM) feedstock powders offer the biocompatibility required for medical implant and device technologies.Design/methodology/approachAM offers a platform to fabricate customized patient-specific parts. Developing feedstock that can be 3D printed into specific 3D structures while providing a favorable interface with the human tissue remains a challenge. Using laser metal deposition, feedstock powder comprising diamond and titanium was co-printed into TiD parts for mechanical testing to determine optimal manufacturing parameters.FindingsTiD parts were fabricated comprising 30% and 50% diamond. The composite powder had a Hausner ratio of 1.13 and 1.21 for 30% and 50% TiD, respectively. The flow analysis (Carney flow) for TiD 30% and 50% was 7.53 and 5.15 g/s. The authors report that the printing-specific conditions significantly affect the integrity of the printed part and thus provide the optimal manufacturing parameters for structural integrity as determined by micro-computed tomography, nanoindentation and biocompatibility of TiD parts. The hardness, ultimate tensile strength and yield strength for TiD are 4–6 GPa (depending on build position), 426 MPa and 375 MPa, respectively. Furthermore, the authors show that increasing diamond composition to 30% results in higher osteoblast viability and lower bacteria count than titanium.Originality/valueIn this study, the authors provide a clear strategy to manufacture TiD parts with high integrity, performance and biocompatibility, expanding the material feedstock library and paving the way to customized diamond implants. Diamond is showing strong potential as a biomedical material; however, upscale is limited by conventional techniques. By optimizing AM as the avenue to make complex shapes, the authors open up the possibility of patient-specific diamond implant solutions.

Arc erosion behaviour of Cu–diamond composites at different load voltages in air atmosphere

ABSTRACT To investigate the arc erosion performance of Cu–diamond composites, Cu–5vol.-% diamond composites were fabricated using the hot-pressing sintering method. Compared to pure copper, Cu–5vol.-% diamond composites exhibited improvements in Brinell hardness of 60.1 HB. The relative density and electrical conductivity of Cu–5vol.-% diamond composites were 97.54% and 83.29% IACS (International Annealing Copper Standard), respectively, with no significant decrease compared to pure copper. The thermal conductivity was 423.48 W·(m·K)−1, showing a slight enhancement. The effect of different load voltages on the arc erosion behaviour of Cu–5vol.-% diamond composites was investigated. Experimental results indicated that as the voltage rose from 3 to 7 kV, the breakdown strength decreased from 7.164 × 106 V m–1 to 2.535 × 106 V m–1, while the arc duration increased from 21.752 × 10−3 s to 28.864 × 10−3 s, and the breakdown current rose from 10.8 to 27.2 A. Additionally, the presence of diamond particles enhanced the viscosity of the molten pool, thus the splashing phenomenon of copper liquid during arc discharge was not obvious, indicating that the material loss was small. Few cracks and holes were detected. The Cu–5 vol.-% diamond composites possess good resistance to arc erosion.

Controlling η phase distribution and its effects on carburized graded cemented carbides via extrusion additive manufacturing

Functionally Gradient cemented carbides (FGCCs) are promising substrates for polycrystalline diamond composite (PDC). Carburization is the mainstream method for preparing FGCCs, but limited carburizing depth often leads to excessive retention of brittle low-carbon phase (η phase) in the core. This study used Powder Extrusion 3D Printing (PEP) to create dual-layered cemented carbide parts with varying thicknesses of low-carbon outer layers. After pre-sintering and carburization, three new FGCCs were produced. Results showed the η phase was confined to the interface region before carburization. With 3.84 mm carbon-depleted layer, the maximum η phase thickness was 1/10 compared to homogeneous FGCCs, with Co gradient of about 4.5 wt%. The two FGCCs with thinner low-carbon layers had smaller Co gradient with no detected η phase. Additionally, the novel FGCCs displayed enhanced fracture toughness in the core. This study achieved controlled η phase distribution, offering new insights for fabricating high-toughness carburized FGCCs without the η phase.

Experimental investigation of nanosecond pulsed laser ablation of polycrystalline diamond composite

A fundamental understanding of the laser ablation of polycrystalline diamond composite (PCD) at different laser energy intensities is indispensable for extending these findings to practical applications where, through appropriate parameter combinations, a substantial amount of material with minimal thermal damage should be removed. The objective of this study is to investigate experimentally the nanosecond ablation of polycrystalline diamond composite at different laser pulse energies and input energy densities. The research comprised two distinct categories of experiments: (1) single-point and (2) line experiments. In single-point tests, the number of the incidence pulses (N.P) was varied from 1 to 100 pulses with different pulse energies (Ep) ranging from 40 to 200 µJ. As the N.Ps increased, the ablation depth increased as well. No considerable enhancement in ablation depth was observed with the increase in pulse energies. For the line experiments, the results emphasized the differences in ablation depths by nearly a factor of 2, resulting in a corresponding change in laser input densities from 6.5 J/mm2 to 1.3 J/mm2. The ablation difference was pronounced as the number of repeats of the scanning path increased. The results emphasize that the ablation depth varies at the same pulse energy when the pulse overlap decreased from 100 % to lower percentages. Based on these results, a constant laser energy density with three different combinations of laser inputs—namely, scanning speed and average power—was selected to evaluate the ablation depth and quality. The results show that in moderate numbers of scan repeats (here 20, 30 & 40 times), it is advisable to adopt a minimum pulse energy when the same ablation depth is achieved compared to higher pulse energies. The ablation pile-up was also evaluated in these repeat ranges, indicating that higher pulse energies and repeats do not result in ablation improvement and cause excessive melt deposition.

Boron-doped diamond composites for durable oxygen evolution

The urgent need to develop efficient, durable, and cost-effective oxygen evolution reaction (OER) catalysts for energy conversion and storage has prompted extensive research. Currently available commercial noble metal-based OER catalysts are expensive and exhibit limited long-term stability. In this study, boron-doped diamond composites (BDDCs) consisting of CoFe and CoFe2C nanoparticles supported by boron-doped diamond (BDD) particles have been prepared. The BDDC catalyst, prepared through a straightforward annealing process, exhibits exceptional durability (up to 72 h at 10 mA cm−2), a low overpotential (306 mV at 10 mA cm−2), and modest Tafel slope (58 mV dec-1). The coherent interfaces between CoFe/CoFe2C nanoparticles and the BDD substrate are essential for enhancing the OER performance. The fabrication method and composite structures presented in this study may facilitate the design and production of promising catalysts.

Effects of Ni–Cr–Mo–Si–B prealloy additives on the properties of Fe-based diamond composites

In this study, Fe-based diamond composites with various Ni–Cr–Mo–Si–B prealloy additives were prepared using hot-press sintering, and the effects of the Ni–Cr–Mo–Si–B content on the relative density, bending strength, Rockwell hardness, and frictional wear properties of the Fe–Cu–Co–Sn matrix were investigated. Additionally, the effect of the composition of the Ni–Cr–Mo–Si–B additives on the interface between the matrix and diamond was studied. The Ni and Cr in the additives facilitated a tight bonding interface without notable gaps between the diamond and Fe–Cu–Co–Sn matrix. Considering the overall performance of the materials, the optimal addition of Ni–Cr–Mo–Si–B was determined to be 10 %, which resulted in notably improved comprehensive performance indicators of the Fe-based diamond composite materials. For example, diamond drill bits made with this formulation exhibited a wear ratio of 1600 mm/g and a penetration rate of 29.21 mm/min, representing increases of 29 % and 44.96 %, respectively, compared to those of drill bits without Ni–Cr–Mo–Si–B additives. Developing high-performance diamond drill bits with increased ROP and extended service lives to enhanced performance, efficiency, and cost-effectiveness in drilling operations across different industries, ranging from mining and construction to oil and gas exploration.

Balling behavior and diamond graphitization of metal-matrix diamond composites by selective laser melting: A quantitative investigation

Selective laser melting (SLM) is an effective and potential technology to prepare metal-matrix diamond composites (MDC). In this study, balling phenomenon and graphitization of diamond of CuSn10-diamond composites by SLM were investigated. By univariate analysis of laser power and scanning speed on the morphology of single track, the balling phenomenon is directly affected by the flowability and wettability of the molten pool. By introducing the concept of laser energy density, balling and diamond graphitization are quantitatively evaluated by the standard deviation σ of surface balling height and IG: ID value, respectively. Balling degree increases with laser energy density, but diamond-graphitization turns out to be the opposite. The CuSn10-diamond composites with low balling and no diamond-graphitization can be obtained at moderate laser energy density of 0.17 J/mm. In terms of performances, bending strength is mainly affected the defects caused by balling, and wear properties is determined by the graphitization of diamond abrasives. Graphitization of diamond results in the transformation of wear mechanism from abrasive to adhesive wear. The optimal properties of 185.36 MPa in bending strength, 0.41 in coefficient of friction and minimum wear loss is obtained in the composite sample prepared at 0.17 J/mm.

A Review of an Investigation of the Ultrafast Laser Processing of Brittle and Hard Materials.

Ultrafast laser technology has moved from ultrafast to ultra-strong due to the development of chirped pulse amplification technology. Ultrafast laser technology, such as femtosecond lasers and picosecond lasers, has quickly become a flexible tool for processing brittle and hard materials and complex micro-components, which are widely used in and developed for medical, aerospace, semiconductor applications and so on. However, the mechanisms of the interaction between an ultrafast laser and brittle and hard materials are still unclear. Meanwhile, the ultrafast laser processing of these materials is still a challenge. Additionally, highly efficient and high-precision manufacturing using ultrafast lasers needs to be developed. This review is focused on the common challenges and current status of the ultrafast laser processing of brittle and hard materials, such as nickel-based superalloys, thermal barrier ceramics, diamond, silicon dioxide, and silicon carbide composites. Firstly, different materials are distinguished according to their bandgap width, thermal conductivity and other characteristics in order to reveal the absorption mechanism of the laser energy during the ultrafast laser processing of brittle and hard materials. Secondly, the mechanism of laser energy transfer and transformation is investigated by analyzing the interaction between the photons and the electrons and ions in laser-induced plasma, as well as the interaction with the continuum of the materials. Thirdly, the relationship between key parameters and ultrafast laser processing quality is discussed. Finally, the methods for achieving highly efficient and high-precision manufacturing of complex three-dimensional micro-components are explored in detail.

Anomalously strong size effect on thermal conductivity of diamond microparticles

Diamond has the known highest thermal conductivity of around 2000 W m−1 K−1 and is, therefore, widely used for heat dissipation. In practical applications, synthetic diamond microparticles are usually assumed to have similar thermal conductivity to that of bulk diamond because the particle size is larger than the theoretical phonon mean free path, so that boundary scattering of heat-carrying phonons is absent. In this report, we find that the thermal conductivity of diamond microparticles anomalously depends on their sizes. The thermal conductivity of diamond microparticles increases from 400 to 2000 W m−1 K−1 with the size growing from 20 to 300 μm. We attribute the abnormally strong size effect to the long-range defects during the growth process based on analysis of point defects, dislocations, and thermal penetration depth dependence of thermal conductivity. Our results play a vital role in the design of diamond composites and in the improvement of the thermal conductivity of synthetic diamonds.

Orientation-dependent tribological behavior of the graphite–diamond composite

Coherent interfacial graphite–diamond composite (Gradia) is superhard and conductive, promisingly applied as electric contact material. In this work, large-scale atomistic simulations were performed to investigate its tribological behavior. Depending on the orientation between graphite–diamond interface and loading direction, three structural evolution modes were observed under compression, featuring Gradia to diamond, Gradia to graphite, and Gradia to defective carbon. Coefficient of friction and wear rate were found orientation-dependent. Orientations of graphite-, diamond-, and defective-preferred structural evolution showed different performance. A satisfied balance between tribological performance and conductivity (rich of sp2-carbon) is obtained in the defective-preferred orientation. These results demonstrate the great potential for Gradia using in dynamic electrical contact and provide a theoretical basis for further material design.

Manufacturing and characterization of functionally gradient material from cemented carbide to diamond via filament-based material extrusion 3D printing

Functionally gradient material (FGM) fabricating via additive manufacturing draws great attention on alleviating the abrupt material discontinuity at the interface of different materials. Introducing gradient structure into polycrystalline diamond composites to produce diamond/cemented carbide FGM is an effective method to reduce the residual stress and enhance the bonding strength of diamond layer and cemented carbide substrate. However, achieving a smooth transition of material properties from cemented carbide to diamond is challenging. In this research, diamond/cemented carbide FGM with a well-controlled gradient was manufactured via filament-based material extrusion. Initially, green bodies of diamond/cemented carbide FGM were obtained by printing with customized composite filaments. Subsequently, thermal decomposition characteristic of the printing filament was analyzed by TGA, and the influence of different heating rates during the binder decomposition stage on the morphology and structure of the green bodies was investigated. After debinding, diamond/cemented carbide FGM without flaw was synthesized at 6.5 GPa and 1550℃. Subsequently, microstructure characterization was performed to investigate the distribution characteristics of the materials inside the diamond/cemented carbide FGM. A continuous transition from tungsten carbide to diamond was achieved inside the gradient layer. Furthermore, the stress state of diamond in different positions of the diamond/cemented carbide FGM was analyzed by Raman spectroscopy. It was found that all the residual stresses in the axial interface of the gradient layer were compressive stress, which can prevent occurrence of microcracks resulted from the tensile stresses formed in the interface. Finally, the impact tests reveal that gradient structure is conductive to improving the bond strength between PCD layer and cemented carbide substrate as the impact times before fracture of diamond/cemented carbide FGM has been increased by 15 %. The gradient structure design strategy, generated via the filament-based material extrusion technology, pioneers new ideas to the development of high-performance FGMs in mass production.

Effects of different binder systems on the characteristics of metal-based diamond composites fabricated via fused deposition modeling and sintering technology

In material extrusion of metal-based composites, binder system plays a vital role and its performance directly influences the quality of the final product and process efficiency. Despite different binder systems have been produced, most studies only concentrated on single binder system without comparison between different binder systems. In this work, two different binder systems were used to fabricate metal-based diamond composites by fused deposition modeling and sintering technology. Morphology of printed metal-based composites samples were compared. Thermal properties of composites samples with different binder systems were analyzed via TG-DSC test, and debinding was carried out at heating rate of 5 °C/min and 2 °C/min, respectively. Then the brown samples were densified via hot-pressing sintering, and the sintered samples were evaluated by scanning electron microscopy, hardness tester and universal testing machine. During the printing process, the feedstock using TP-based binder system exhibited better printing performance compared with that using the PW-based binder system. The results also revealed that appropriate nozzle temperature should be determined according to the thermal properties of the feedstocks so as to minimize printing defects. The debinded samples with different binder systems can retain structural integrity when the heating rate controlled properly. As for the samples after sintering, it has to be highlighted that the hardness on the top surface of the sintered sample was higher than the hardness on the side because of different deposition characteristics. In addition, the samples using TP-based binder presented a more uniform microstructure and thus obtained better flexural strength and relative density. It can be concluded that the TP-based binder is preferable as it contributes to better performance of the metal-based diamond composites compared with the PW-based binder.

Thermal-mechanical evolution behaviors of metal matrix diamond composite by powder bed fusion-laser beam

The thermal damage of diamond and the residual stress have always been the critical issues to be resolved in the development of metal matrix diamond composites. In the presented study, FeCoCrNi high entropy alloys (HEAs)-diamond composites were fabricated by powder bed fusion-laser beam of metals (PBF-LB/M), using un-coated diamond and Ti–Ni coated diamond, respectively. Based on the numerical and experimental analysis, the effect of thermal-mechanical behavior on the microstructures and mechanical properties of the composites was systematically investigated. By establishing the temperature field of the PBF-LB molten pool, the defects, diamond graphitization and in-situ TiC formation were studied. The start-temperature for diamond graphitization in coated samples was 365 °C higher than that of un-coated samples, due to the diffusion barrier effect of TiC. Subsequently, by thermo-mechanical coupling, the property and value of the residual stress exhibited sudden change at the diamond/matrix interface. The TiC intermediate layer significantly relieved the stress concentration at interface, and effectively avoided cleavage fracture of the diamond and the initiation of interfacial cracks. At the moderate molten-pool temperature, the coated diamond composites exhibited optimal performance, as bending strength of 913 MPa, friction coefficient of 0.25 and worn mass loss of 0.67 mg. Finally, the quantitative relationship between PBF-LB molten-pool temperature and the relative density, graphitization degree, residual stress, retention(bending strength) and wear performance was established, to demonstrate the thermal-mechanical evolution of the HEAs-diamond composites by PBF-LB.

Tribological behavior of PDC-cutter including cemented carbide and polycrystalline diamond composites produced by HPHT for drilling applications

In this study, the tribological behavior of PDC-cutter including WC particles/Ta-20Nb binder composite as substrate and polycrystalline diamond composite as PCD layer produced by high pressure-high temperature (HPHT) for drilling applications was investigated. To examine the metallurgical behavior, phase analysis, hardness of substrate and PCD layer, and tribological behavior, scanning electron microscopy, X-ray diffraction, Vickers microhardness, and wear tests were used, respectively. Due to the HPHT of the manufacturing process, the high hardness of the interfaces, especially for the WC/Ta-20Nb was achieved, which had ∼28% higher hardness than the diamond grits/Ta-20Nb binder. Therefore, no obvious porosity was observed in the interfaces and the composites were completely densified because the particles had good retention strength. The wear results showed that the tribological behavior of PCD layer/granite or marble pairs was directly influenced by the binder content, with samples having a lower binder content showing superior wear performance. Additionally, worn surface investigations demonstrated that adhesive and abrasive wear mechanisms were present in all pairs, with their intensities being strongly correlated with the binder concentration.

Numerical simulation and experimental investigation of the molten pool evolution and defects formation mechanism of Selective laser melted CuSn20/Diamond composites

Some defects such as small pores, thermal damage of diamond particle and micro-cracks between diamond and metal matrix existed in SLM-fabricated metal-bonded diamond tools. For further application, it is vital to understand the formation mechanism of such defects by SLM-fabricated parameters. In this work, a multiphysics field numerical simulation model based on computational fluid dynamics (CFD) was developed to investigate molten pool evolution and defects formation mechanism for SLM-fabricated CuSn20-bonded diamond composites. From simulation results, the metal particles melt and flow forward under the action of the laser. Also, the presence of diamond particles can obstruct the normal flow of melted CuSn20 fluid. Increasing the laser power can widen and stabilize the molten pool, however, exacerbate the thermal damage of diamond particles. Specially, the migration and marginalisation of the diamond particles during the formation of molten pool were found by simulation and experimental results. Unavoidably, there are obvious gaps in the interfacial bonding region of diamond and CuSn20 due to the comprehensive reasons of thermal gradient, differences in thermophysical properties of two materials and undergo continuous migration and rotational behavior of diamond particles. These findings have potential value for understanding and optimizing the process of SLM-fabricated metal-bonded diamond tools.