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Metal-matrix-impregnated diamond composites are used for fabricating many kinds of diamond tools. In the efforts to satisfy the increasing engineering requirements, researchers have brought more attention to find novel methods of enhancing the performance of impregnated diamond composites. In this study, deep cryogenic treatment was applied to Fe–Co–Cu-based diamond composites to improve their performance. Relative density, hardness, bending strength, and grinding ratio of matrix and diamond composite samples were measured by a series of tests. Meanwhile, the fracture morphologies of all samples after the bending strength test were observed and analyzed by scanning electron microscope. The results showed that the hardness and bending strength of matrix increased slightly after deep cryogenic treatment. The grinding ratio of impregnated diamond composites exhibited a great increase by 32.9% as a result of deep cryogenic treatment. The strengthening mechanism was analyzed in detail. The Fe–Co–Cu-based impregnated composites subjected to deep cryogenic treatment for 1 h exhibited the best overall performance. [ABSTRACT FROM AUTHOR]

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. [ABSTRACT FROM AUTHOR]

Specifically, data for sample D3 in Figure 1 in this Article is the same as data in Figure 2 in[1]; data in Figure 2a in this Article appears identical to data in Figure 4a in[1] with the exception that data in this Article contains additional C-C peaks that seem to have been removed in[1]; data in Figure 7a in this Article appears to be identical to data in Figure 4b in[1] with the exception of being shifted by approximately 6eV. The Editors were not able to obtain current contact details for Youhong Sun, Ming Qian, Baochang Liu, Ke Gao, Yinlong Ma, Mao Wen & Weitao Zheng. The Editors no longer have confidence in the data reported in this Article. [Extracted from the article]

The particle size and particle size ratio of the raw diamond powder have a great influence on the stacking density, which is critical to the performance of polycrystalline diamond compact (PDC). In this study, diamond powders with five different particle size of 1 μm, 4 μm, 12 μm, 20 μm and 27 μm were selected. High stacking density diamond powder formulations with three filler particle ratios of 10 wt%, 20 wt% and 30 wt% were designed by using 12 μm, 20 μm and 27 μm diamond as the main particles and 1 μm and 4 μm diamond as the filler particles. The different formulations were evaluated by mechanical property tests and microscopic characterization of PDC samples to find out the optimal filler particle size as well as filler ratio in different main particle series. The results showed that the larger the main particle size in the formulation, the worse the wear resistance and the better the impact toughness of PDC. Adding decent number of fine particles with appropriate particle size could effectively improve the comprehensive performance of PDC. But the match between different main particles and filler particles was not consistent, and the three optimal formulations finally derived under the conditions in this paper were 80 wt%12 μm-20 wt%1 μm, 90 wt%20 μm-10 wt%4 μm, and 80 wt%27 μm-20 wt%4 μm. The rock cutting life of PDC with optimal formulations was all improved by 20 passes and the wear resistance was improved by 62%, 53.8% and 40.4%, respectively, compared with the single particle size control group. The impact toughness was improved by 650 J/68.4%, 1200 J/77.4% and 750 J/20%, respectively. The PDC performance variation pattern of different formulations was highly consistent with that of Co content, indicating that the decrease of Co content caused by the increase of stacking density was the main mechanism for performance enhancement of dual-particle size PDC. • PDCs with different dual particle size diamond formulations were fabricated. • The matching of different main particles with filler particles was elucidated. • Optimal diamond powder formulations were derived for three different main particles. • The link between mechanical properties and Co content of PDC with different formulations was elucidated. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond compacts (PDC) with three different substrate geometries and trimodal diamond particle formulation were fabricated. The properties of prepared PDC including Vickers hardness, toughness, wear performance, and thermal stability were evaluated. The microscopic features including morphology, elemental and phase composition, and residual stress state were systematically investigated. The optimal substrate contributing to best comprehensive properties of PDC was singled out. Discrepancies in the properties of PDCs with different substrate geometries were mainly in fracture toughness and impact toughness, with maximum and minimum values of 6.54 MPa m1/2/3120 J and 5 MPa m1/2/1680 J, respectively. The best wear performance was 5.88 mm2/60P. The results showed that the tendency of wear performance was consistent with toughness and thermal stability, showing a strong correlation. The substrate geometry affected the morphology and composition of the cobalt transition layer in the interface, which had a significant impact on its toughness. Differences in residual stress states induced by the interfacial geometries were also important determining PDC's impact toughness. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond compact (PDC) with different grain sizes were fabricated and the multi-physical behaviors, including mechanical-, thermal-, and magnetic performances, and the microscopic features were examined to study the grain size dependence of wear behavior while cutting dense granite. The results showed that the coarse grade PDC had higher impact resistance and fracture toughness. However, the fine grade PDC had higher cobalt content, hardness and thermal resistance. Among these properties, the wear resistance changed the same way as thermal expansion properties proving the strong correlation. Moreover, the crack network caused by thermal mismatch, and the peeling/fracture of metallic phases and diamond promoted fracture wear and played the critical roles in the wear of coarse grade PDC. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond compact (PDC) cutters are used widely for mining and drilling in soft to medium hard rock formations. During drilling in very hard and strong rock formations, the rapid wear of the polycrystalline diamond layer results in a low service life of drilling bits. To improve the performance of PDC cutters, we adopted a high-temperature, high-pressure (HTHP) sintering method (5.5–6.0 GPa and 1350–1500 °C) in the current research by adding a certain amount of graphene to raw materials, and we successfully prepared a new type of high-performance diamond composite PDC-G (graphene was added to PDC). We investigated the microstructure, residual stress, hardness, wear resistance, thermal conductivity, and electrical conductivity of the as-synthesized PDC-G. Compared with PDC without graphene, the hardness and wear resistance of PDC-G with 0.1 wt% graphene addition were enhanced by 75% and 33%, respectively. Moreover, the electrical conductivity of PDC prepared by graphene strengthening was improved 42-fold. The strengthening mechanism of PDC-G mainly occurred as a result of the lubricating effect of graphene between diamond particles; hence, a more dense and uniform structure was formed in the polycrystalline diamond layer after HTHP sintering. [ABSTRACT FROM AUTHOR]

In this study, fine-grained (0-2 μm) polycrystalline diamond compacts (PDC) doped with 0.5 wt% nano‑vanadium carbide (VC) addition were sintered under high pressure and high temperature (HPHT, 6GPa and 1600 °C). The effect of VC on the phase composition, microstructure and mechanical properties of fine-grained PDC has been systematically studied. The results showed that the hardness and impact resistant energy of the PDC samples doped with VC were 66.65GPa and 160 J, increased by 8.7% and 100%, respectively. The samples exhibited higher wear resistance, and the wear ratio of 5 passes, 10 passes and 15 passes were 60 × 104, 54.3 × 104 and 52.2 × 104，increased by 8.2%, 65.4% and 65.5%, respectively. The enhanced of hardness and wear resistance can be attributed that VC as a harder material occupied the space of cobalt in the polycrystalline diamond table and reduced the cobalt and η-phase Co 3 W 3 C content. At the same time the VC refined the tungsten carbide (WC) gains and made them more homogeneous dispersed in the polycrystalline diamond table. VC and WC formed solid solution dispersed in the binder to produce the pinning effect, which change the fracture mode to improve the impact resistance of PDC. [Display omitted] • Doping VC reduced the content of cobalt and η-phase Co 3 W 3 C in PDC. • Doping VC refined the WC grains in the PDC significantly. • Doping VC enhanced the mechanical properties of fine-grained PDC. • VC and WC formed the solid solution (V,W)C X which changed the fracture mode. [ABSTRACT FROM AUTHOR]

With the increased difficulty of drilling into hard rock in the petroleum industry, the demand for higher performance and efficiency of impregnated diamond bits (IDB) has risen sharply. This paper describes the effect of Mo 2 C coatings on the wear properties and working efficiency in Fe-Ni-WC-based IDBs. The Mo 2 C-coated diamonds were obtained via the molten salts method. The diamond/Fe-Ni-WC IDBs were prepared by vacuum hot-press sintering method. Laboratory drilling tests of IDBs were carried out to evaluate the wear performance of the two drilling bits. An ultra-depth field 3D imaging microscope was performed to measure the protrusion height of diamond particles on the bottom surface of IDBs. The results manifested that the addition of the Mo 2 C coating contributed to increasing the protrusion height of diamonds, meaning the enhancement of the interface strength between the diamonds and matrix. The drilling rate of the Fe-Ni-WC-based IDB with Mo 2 C-coated diamonds is 18% higher than that of Fe-Ni-WC-based IDB with uncoated diamonds, accompanied by increased wear loss. • An impregnated diamond bit with Mo 2 C-coated diamond is developed. • The breakage rate of the Mo 2 C-coated IDB is 37% less than that of uncoated IDB. • High-strength Mo 2 C interface improves diamond protrusion height. • The drilling rate of Mo 2 C-coated IDB is 18% higher than that of uncoated IDB. [ABSTRACT FROM AUTHOR]

A WC-bronze-based matrix and an impregnated diamond composite (IDC) reinforced by nano-NbC were fabricated through powder metallurgy to improve the lifespan of drilling bits. The density, hardness, bending strength, and wear resistance of the matrix and IDC were studied. The microscopic features were examined by scanning electron microscopy and X-ray diffraction. The results showed that when the nano-NbC content was 5 wt%, the hardness and bending strength of matrix were 43 HRC and 1085 MPa, increased by 26% and 28%, respectively. The IDC exhibited higher bending strength and the highest wear resistance, and the grinding ratio was 1150, which was approximately 2.4 times higher than that of IDC without the addition of nano-NbC. The indoor drilling tests showed that the drilling bit life expectancy was 78 m, improved by 70%. The enhanced compactness characteristics, grain refinement, and dispersion strengthening were the main reasons behind the enhanced properties. [Display omitted] • Nano-NbC reinforced WC-bronze-based impregnated diamond composites were fabricated. • The composites reinforced by nano-NbC exhibited better mechanical properties. • The life expectancy of drilling bits improved obviously via nano-NbC addition. • The microstructures and phase composition of composites were analysed in detail. • The strengthening mechanisms of nano-NbC were clarified. [ABSTRACT FROM AUTHOR]

Ti-coated diamond and cBN with TiCN as the binder were used to fabricate the TDBN-TiCN series PDC with improved heat resistance, wear resistance and impact toughness by a China-type cubic high-pressure apparatus (5.5–6.5 GPa, 1450–1650 °C) for drilling. Under high temperature and high pressure conditions, the Co in the cemented carbide substrate penetrated into the PCD layer and the binder TiCN to form a metal-ceramic binder system. It can promote the formation of polycrystalline cubic boron nitride (PcBN) from cubic boron nitride particles at the grain boundaries, and promote the TDBN-TiCN series PDC to have the performance of PCD and PcBN. Compared with the TDBN series PDC developed by our former research, the wear resistance of TDBN-TiCN series PDC increased by 17% and the impact toughness increased by 26%. In the TDBN-TiCN series PDC, some heat resistant phases, such as PcBN, TiB 2 and TiN, were formed so as to enhance the initial graphitization and oxidizing temperatures to 958 °C, which was 8 °C higher than the TDBN series PDC (950 °C) and 178 °C higher than conventional PDC (780 °C). • The Co in the cemented carbide substrate penetrated into the PCD layer and TiCN to form a metal-ceramic binder system. • The polycrystalline cubic boron nitride (PcBN) from cubic boron nitride particles at the grain boundaries. • PcBN, TiB 2 and TiN, were formed so as to enhance the initial graphitization and oxidizing temperatures to 958°C. [ABSTRACT FROM AUTHOR]

Ti-coated diamond with different particle sizes and proper amounts of cubic boron nitride (cBN) was used to fabricate polycrystalline diamond composite (PDC) with improved wear resistance and thermal stability under high temperature and high pressure (5.5–6.5GPa, 1500–1650 °C). The ratio of Ti-coated diamond powder, cBN powder and normal diamond powder was W 30 – 50 : W 4 – 8 : W 0 – 1 = 70: 15: 15. Cobalt (Co) was used as a binder, and cemented tungsten carbide was used as a substrate to sinter a new high-performance PDC. Ti and TiC on the surface of Ti-coated diamond reacted with cBN under high temperature and high pressure to generate new ceramic phases such as TiB 2 , TiN and TiN 0.3 , which have high hardness and good wear resistance. Compared with the conventional PDC, the impact toughness and wear resistance of PDC with Ti-coated diamond and cBN addition were enhanced by 19% and 28%, respectively. The ceramic phase acts as a protective barrier, which enhances the initial graphitization and oxidizing temperature to 942–950 °C, which were 162–170 °C higher than the conventional PDC. The new ceramic barrier wrapped around the surface of the diamond and Co after the formation of the D-D (diamond-diamond) bonding will give priority to the oxidation reaction of Co and diamond with oxygen, which prohibits cobalt-catalytic graphitization of diamond, meeting the needs of PDC thermal stability and wear resistance in the field of drilling. • A new type of PDC was HPHT sintered with Ti-coated diamond and cBN. • Thermal and wear resistant ceramics such as TiB 2 , TiN and TiN 0.3 was generated during HPHT sintering. • The initial oxidizing temperature of the new PDC was about 950 °C. • The impact toughness and wear resistance of new PDC increased by 19% and 28, respectively. [ABSTRACT FROM AUTHOR]