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Polycrystalline cubic boron nitride (PcBN) composites were prepared through high-temperature and high-pressure (HTHP) sintering process. Cubic boron nitride (cBN) powders with particle sizes of 0.2, 1, 3, and 8 μm were selected as raw materials, and Al-Co-TiN was employed as a binder. The effect of particle size of initial cBN powders on the microstructure, relative density, flexural strength, microhardness, fracture toughness and abrasive ratio of sintered PcBN composite were systematically studied. The results showed that synthesized products were mostly made of cBN, TiN, AlN, TiB2 and CoN phases. The mechanical properties of sintered PcBN composites first increased and then decreased with a reduction in the particle size of cBN powders. When the particle size of initial cBN powder was 1 µm, the binder was observed to be evenly distributed around the cBN grains in the sintered product. Moreover, there was a close bonding between cBN grains and the binder in the sintered product when the particle size of initial cBN powders was 1 µm, consequently, the optimal mechanical properties were achieved. The maximum values for relative density, flexural strength, microhardness, fracture toughness and abrasive ratio were 99.1%, 607 MPa, 47.06 GPa, 6.52 MPa·M1/2 and 7125, respectively. [ABSTRACT FROM AUTHOR]

Metal cutting processes contribute significant share of the added value of industrial products. The need for machining has grown exponentially with increasing demands for quality and accuracy, and despite of more than a century of research in the field, there are no reliable and accurate models that describe all the physical phenomena needed to optimize the machining processes. The scientific community has begun to explore hybrid methods instead of expanding the capabilities of individual modelling schemes, which has been more efficient than efficacious direction. Following this trend, we propose a hybrid finite element — machine learning method (FEML) for modelling metal cutting. The advantages of the FEML method are reduced need for experimental data, reduced computational time and improved prediction accuracy. This paper describes the FEML model, which uses a Coupled Eulerian Lagrangian (CEL) formulation and deep neural networks (DNN) from the TensorFlow Python library. The machining experiments include forces, chip morphology and surface roughness. The experimental data was divided into training dataset and validation dataset to confirm the model predictions outside the experimental data range. The hybrid FEML model outperformed the DNN and FEM models independently, by reducing the computational time, improving the average prediction error from 23% to 13% and reduced the need for experimental data by half. [Display omitted] • A Novel Hybrid FEML model based on Deep Neural Networks (DDN) and Finite Element Method (FEM) is proposed for predicting metal cutting process outcomes. • Hybrid FEML model outperforms DNN and FEM models independently regarding prediction accuracy, computational time and need for experimental data. • FEM model with CEL formulation has advantages in 3D machining simulations over ALE methods because CEL does not require remeshing. [ABSTRACT FROM AUTHOR]

Boron nitride has attracted scientific interest in recent years due to its potential use in electronics, both as hexagonal (hBN) and cubic (cBN) phases. While both are successfully realized through chemical vapor deposition, the heteroepitaxial growth of cBN on another iconic semiconductor, diamond is plagued with mixed‐phase formation. Employing first‐principles computations and a nanoreactor approach, the BN phase preferences are explored on diamond (001) controlled—as it is discovered—by the hydrogen gas concentration. In a limited‐hydrogen environment, the initial BN‐island expands along the diamond surface, forming a 3D metastable cubic phase that grows in the direction normal to the basal plane through kinetically‐limited nucleation, thus overcoming the thermodynamic preference toward the hBN phase. Comparatively, the amorphous phase is favored in the absence of hydrogen, while the hexagonal phase dominates at its high levels, elucidating numerous experimental observations. A obtained kinetic phase diagram connects the phase with hydrogen chemical potential to facilitate targeted phase selection. The results suggest that gas‐mediated nucleation kinetics provide feasible control for the precise synthesis. It also offers valuable guidance for the controllable synthesis of desired BN phases and advances research toward potential BN electronics. [ABSTRACT FROM AUTHOR]

Machining of metal matrix composites (MMC) is a challenging process as they are difficult to cut and cutting tools get worn out in a short time. In this paper, the performance of two industrial carbide grades and a cubic boron nitride (CBN) tool are assessed when machining of AZ91/SiC composites. Mg-based composites with different volume fractions and particle sizes are machined at various cutting conditions to evaluate the tools wear resistance and finished surface. The surface of the worn-out tools and machined samples are analyzed by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and roughness tester. Results revealed that the tool wear increased for composites reinforced by smaller particles regardless of the tool type. Additionally, tool grade TH1000 resulted in longer tool life when machining of Mg-based composites compared to the CP500 grade so that at a cutting speed of 70 m/min and feed rate of 0.1 mm/rev, tool life improved nearly 250%. CBN tools showed the best performance when machining of Mg-based composites as tools became worn out after 255 s which is considerable compared to carbide tools. Also, the finished surface caused by cemented carbide CP500 indicated the worst quality. [ABSTRACT FROM AUTHOR]

Phase-pure crystalline cubic boron nitride (c-BN) thin films are of immense scientific and technical interest because of their suitable properties for optoelectronic and high-power applications, high thermal conductivity and hardness, chemical inertness to ferrous materials in high-temperature and caustic environments, and high optical transmittance over a broad wavelength range from the ultraviolet (UV) to the visible spectrum. However, the lack of controlled fabrication techniques for high-quality c-BN films significantly affects the reliable practical applications of this material. Recently, phase-pure single-crystal c-BN and a new phase of BN with unique properties, called quenched-BN (Q-BN), have been synthesized using a pulsed laser annealing (PLA) technique to overcome the current impediments in c-BN synthesis. This review paper comprehensively examines the current status of analytical research on the growth, characterization, and properties (optical and electrical) of c-BN films fabricated by different synthesis techniques, with a particular emphasis on the immensely promising PLA technique. In particular, the paper focuses on the processes used to obtain phase-pure c-BN films via epitaxial growth, characterization of defects and interfaces, and control of the structural, electrical, and optical properties of these films by controlling the growth parameters, including the laser–solid interaction for the direct conversion of nanocrystalline hexagonal boron nitride (h-BN) into crystalline c-BN using the PLA technique. The latest developments in c-BN electronics are also discussed, with a focus on producing p-and n-type conductivity using different dopants to achieve dopant concentrations far beyond the retrograde thermodynamic solid solubility limits. Finally, the future prospects and possible applications in emerging areas are discussed, as well as the goals and guidelines for future research of PLA-grown c-BN films. A comprehensive overview of the properties, application, characterization, shortcomings, and future prospects of c-BN [ABSTRACT FROM AUTHOR]

AlN/h-BN composite ceramics exhibit considerable anisotropy, which significantly constrains their application in areas such as semiconductor packaging and light-emitting diodes. The introduction of c-BN can significantly enhance mechanical properties and effectively reduce the anisotropy. However, this results in lower thermal conductivity, which is important issue that needs to be addressed. In this study, hot-press sintering was employed to fabricate AlN-10 wt% h-BN-15 wt% c-BN- x wt.% Y 2 O 3 (AB15C x Y, with x = 0, 1, 2, 3, 4) composite ceramics. Effects of Y 2 O 3 content on microstructure, anisotropy, thermal conductivity, and flexural strength of AlN/BN composite ceramics were systematically investigated. Results indicate that during high-temperature sintering, c-BN undergoes phase transformation into "onion-like'' h-BN, and Y 2 O 3 reacts with Al 2 O 3 film on the surface of AlN powder to form Y 3 Al 5 O 12 (YAG) phase. YAG phase promotes sintering densification as well as directional arrangement of lamellar h-BN, endowing composite ceramics with relative density of 99.6 % (sample AB15C1Y) with increased degree of anisotropy (the index of orientation preference is | IOP | = 68–93). Thermal conductivity of AlN/BN composite ceramics is directly correlated with lattice oxygen content, and as Y 2 O 3 content increases, lattice oxygen content decreases monotonically. Lattice oxygen content of sample AB15C3Y is as low as 0.35 wt%, and the maximum values of K ∥ and K ⊥ are 100 and 59 W‧m−1‧K−1, respectively, which represent increases of 64.8 % and 51.3 % compared with those of AB15C0Y ceramic, respectively. With the increase in Y 2 O 3 content, AlN grains become gradually larger, and the proportion of YAG phase, which is characterized by brittle grain boundaries, increases, leading to gradual reduction in the flexural strength of AlN/BN composite ceramics. [ABSTRACT FROM AUTHOR]

The cubic boron nitride (cBN) single crystals present a higher expectation for deep ultraviolet (DUV) detectors. Simulations have been carried out using Synopsys TCAD to improve the performance of detectors. The light and dark current were observed by changing the parameters such as electrode spacing, doping concentration. The detector has the maximum response with the doping concentration of 1013 cm−3. The light-to-dark current is up to about 60 with an electrode width and spacing of 15 µm. The photocurrent was measured based on the prototype device. [ABSTRACT FROM AUTHOR]

The lithium-based cubic boron nitride (c-BN) system contains three key components: the reactant hexagonal boron nitride (h-BN), the catalyst lithium boron nitride (Li3BN2), and the synthetic product c-BN. Ab initio methods are performed to replicate the structural, thermodynamic, and phase stability characteristics of the three phases (c-BN, Li3BN2, and h-BN). The quasi-harmonic approximation is used to generate the p-T phase diagrams for the three key phases. The c-BN is determined to be the most thermodynamically stable among the three phases at room temperature. The heat capacities for c-BN, Li3BN2, and h-BN converge to values of 208.25, 43.86, and 338.86, J·mol−1·K−1, respectively. As c-BN has a greater bulk modulus, the frequencies in the acoustic area of the phonon dispersion are higher. From the p-T phase diagrams, the temperature and pressure needed for the h-BN/c-BN phase transition are less than those needed for the decomposition of Li3BN2. More advantageous than the Li3BN2 to c-BN pathways is the direct conversion of h-BN to c-BN. [ABSTRACT FROM AUTHOR]

"Lamellar" structure of hexagonal boron nitride (h-BN) is prone to the formation of pore defects and the establishment of directional alignment during sintering process, which lead to AlN/BN composite ceramics exhibiting low density and anisotropic flexural strength (σ ≡ , σ ⊥ , and σ ∥) (Orientation Bias Index |IOP| ≫ 1); these factors greatly limit the application of AlN/BN composite ceramics. In this work, cubic boron nitride (c-BN) was introduced as a reinforcing phase into AlN/BN composite ceramics, which were prepared via hot pressing sintering, and the effects of c-BN addition on microstructure, mechanical properties, and anisotropy were systematically investigated. The results show that during hot pressing sintering, c-BN phase changes into h-BN with "onion" structure, which effectively fills pore defects and reduces the degree of alignment of h-BN. |IOP| of sample 0C25H (170) continues to decrease with the increase in c-BN amount up to 2.7%. and anisotropy is significantly reduced. With the increase in c-BN amount, σ ≡ and σ ⊥ first increase and then decrease, while σ ∥ only increases. σ ≡ and σ ⊥ reach the highest values (σ ≡ = 362 MPa and σ ⊥ = 340 MPa) at a c-BN amount of 15% (sample 15C10H); these values are 20.5% and 15.6% higher than those of sample 0C25H (no c-BN added), respectively, and σ ∥ reaches the highest value (σ ∥ = 239 MPa) for sample 25C0H, which is 136.6% higher than that of sample 0C25H. Sample 25C0H exhibits the highest σ ∥ value (239 MPa), which is 136.6% higher than that of sample 0C25H. The onion-like h-BN formed by phase transformation of c-BN not only provides significant toughening to AlN/BN composite ceramics but can also effectively reduce anisotropy in their mechanical properties. [ABSTRACT FROM AUTHOR]

The resonant frequencies of natural oscillations in disk-shaped specimens are determined as a function of the elasticity modulus and dimensions of a specimen. The effect produced by the specimen fastening place on the precision of measuring the elasticity modulus and the decrement of oscillation in the series of cubic boron nitride/diamond polycrystal specimens are estimated. All the considered variants of sintered polycrystals can be classified into three groups depending on the diamond powder content. The properties (elasticity modulus, oscillation decrement, sound velocity, Q factor) are different for each of these groups of polycrystals. [ABSTRACT FROM AUTHOR]

A mathematical model is developed for the technological process of synthesis under conditions of high pressures P and temperatures T of a polycrystalline superhard material based on cubic boron nitride (cBN). The superhard material is obtained from a wurtzite boron nitride (wBN) powder modified with aluminum Al, which is the initiator of the wBN→cBN phase transformation process. As a result of modelling, the boundary parameters Р and Т of the superhard material synthesis and the required amount of aluminum addition are calculated. It has been established that the synthesis of a material with a hardness of 28–30 GPa and crack resistance in the range of 7–10 MPa·m1/2 is carried out in the pressure range of 5–7 GPa at temperatures of 2.100–2.250 °C, and the aluminum additive content should be 7.5–10.0 wt.%.

Cubic boron nitride (CBN) tool is one of the most extensively used tools in modern industrial processing and manufacturing. The service life of CBN tools has extraordinary significance for machining efficiency and surface finish of workpieces. Here, we investigated the tribological behaviors of CBN/Si 3 N 4 pairs to simulate the process of CBN tools cutting ceramics and demonstrated that the use of optimal 0.02 wt% non-toxic and eco-friendly hexagonal boron nitride (hBN) aqueous solution as a water-based cutting fluid enabled to reduce the wear rate of CBN by ∼64%, and improve the material removal of Si 3 N 4 by ∼13% compared to pure water lubrication. Further analysis indicated that the physical adsorption of hBN nanosheets played a dominant role in the lubrication at the sliding interface where the direct contact of interfacial asperities was separated and then the tribochemical reactions of CBN with water were suppressed. The results help in the development of environmentally friendly lubricants to match the requirements of mechanical processing for difficult-to-machine materials. [ABSTRACT FROM AUTHOR]

Lead glaze possess excellent radiation ray shielding ability, and it is an efficient way to stop radiation spillover by using lead glazed indoor titles in a building. The merit of low firing temperature of lead glaze is, however, associated with its poor wear resistance. Here super-hard cubic boron nitride (cBN) particles, of a neutron shielding property, are introduced into the soft glass matrix to improve its mechanical properties. Results show that, at meticulously tailored conditions, the lead glaze surface is successfully enriched with cBN particles due to the lower density of cBN relative to the glaze. With 5 wt% cBN particles embedded in the glass matrix, the hardness increases by 51.2% and more importantly, the glaze yields significantly improved wear resistance. The finite element analysis reveals that the cBN particles enhance the toughness of the glaze, a key factor to wear resistance, by reducing the crack tip stress concentration. [ABSTRACT FROM AUTHOR]

The results of thermodynamic modeling of superhard materials based on cubic boron nitride (cBN) with a tantalum nitride (TaN) binder and additions of aluminum, as well as microfibers of various physicochemical nature (oxide (Al2O3, Mg2B2O5) and non-oxide (SiC, Si3N4)), are presented. The theoretically calculated chemical interactions between the components of superhard composite materials are experimentally verified. The chemical nature of the microfibers significantly affects the reaction interaction between the cBN matrix material and TaN binder in the presence of liquid aluminum, resulting in the formation of tantalum boride. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (CBN) composites frequently serve as tool materials in abrasive machining for surface finishing. The geometric features of individual CBN grains are crucial for both machining stability and the resulting surface quality of workpieces. While the grains, whether embedded in the matrix or exposed on the working surfaces, showcase seemingly 'random' geometric characteristics, they can typically be described through statistical analysis. In this study, three crucial three-dimensional geometric features of the CBN abrasive grains exposed on the working surface of a commercial CBN honing stone were characterized. These features include the protrusion height, inclination angle, and projection angle. In total, 116 abrasive grains identified within the processing zone were individually measured and inspected using a digital microscope and scanning electron microscope. The obtained results underwent statistical analysis and were subsequently compared. The results revealed that the abrasive grains exhibited an average protrusion height of 18.56 μm, an average inclination angle of 35.32°, and an average projection angle of 120.70°. Utilizing the measurement and inspection results, the abrasive grains were categorized into five distinct groups, each corresponding to a different phase in their service life cycle. • CBN grain parameters measured and characterized on an in-service honing stone. • Service life categorized into five phases based on protrusion height and surface integrity. • Morphological characteristics and wear features summarized for each phase. • Protrusion height and inclination angle linked to grain wear; projection angle stable. [ABSTRACT FROM AUTHOR]

The sintering mechanisms and temperature dependence of coalescence of colliding cubic boron nitride (c-BN) nanoparticles are investigated using classical molecular dynamics (MD) simulation. Particle-particle collisions of 2.55-nm octahedral c-BN nanoparticles, consisting solely of the most stable {111} facets, with half of the surface terminations being boron and the other half nitrogen, are analyzed statistically and evaluated to assess the initial temperature range (2500 K – 3100 K) for sintering and its effect on grain growth. At these temperatures, the collision process maximizes contact surface area through interfacial sliding, thereby minimizing free energy and accommodating dangling bonds. Moreover, the exothermic formation of bonds of the coalescing nanoparticles increases the temperature. The alignment of the {111} orientation of the two collided nanoparticles occurs at a temperature slightly above the melting point, and rapid grain growth happens when the temperature is a few hundred degrees higher than that. However, phase separation also takes place at the corners away from the collision plane of the merging nanoparticles. Between 3100 K and 3250 K, crystalline alignment occurs, which aids the sintering process and allows for the formation of a well-structured nanocluster. However, above 3300 K, phase separation dominates and drives the melting of the entire sintered nanocluster. • Initial contact of vertex-to-surface rapidly converts to edge-to-surface followed by surface-to-surface. • Two nanoparticles can slide at sufficiently high temperatures to maximize the contact area for B–N bond formation. • Crystallographic alignment of {111} facets of two nanoparticles can occur upon exceeding the melting temperature at 3000 K. • Coalescence can result in the evolvement of a good mono-crystalline {111} surface, forming a well-structured nanocluster. • Phase segregation engulfs the entire cluster when the temperature exceeds 3200 K. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy is a critical material for turbine engine components in the aerospace application, but the poor machinability and low machining efficiency have further hampered it to be used widely. Cubic boron nitride (cBN), having extreme hardness and chemical inertness, is the potential candidate to process superalloys. In this paper, we systematically investigated the tool wear characteristic of cBN at different cutting speeds in dry turning of Inconel 718 by experiments and FEM simulations. The FEM model with initial flank wear land (VB) was established and validated. Effects of cutting speeds (200–400 m/min) on cBN tool life and wear mechanisms were systematically investigated. Effects of tool flank wear on cBN tool cutting edge temperature field and Inconel 718 machined surface layer stress distribution were analyzed by FEM simulations. [ABSTRACT FROM AUTHOR]

This article deals primarily with the problem of determining the cutting force when machining hardened steels. For this study, the steel used was 100 Cr6, number 1.3505. The secondary aspects of the study focused on the evaluation of the surface quality of machined samples and the recommendation of cutting conditions. A wide variety of components are used in engineering, the final heat treatment of which is hardening. These components are usually critical in a particular product. The quality of these components determines the correct functioning of the entire body of technical equipment, and ultimately, its service life. In our study, these are the core parts of thrust bearings, specifically the rolling elements. The subject of this experiment involves machining these components in the hardened state with cubic boron nitride tools and the continuous measurement of the cutting force using a dynamometer. The machining is carried out on a conventional lathe. A total of 12 combinations of cutting conditions were set. Specifically, for three cutting speeds of 130, 155 and 180 m·min−1, the feed rates of 0.05 and 0.1 mm·rev−1 and the cutting widths of 0.2 and 0.35 mm, were evaluated The evaluation assessed the surface quality by both touch and non-touch methods. A structural equation with the appropriate constants and exponents was then constructed from the data obtained using the dynamometer. The experiment confirmed the potential of achieving a value of the average arithmetic profile deviation Ra in the range of 0.3–0.4 when turning hardened steels with cubic boron nitride. [ABSTRACT FROM AUTHOR]

Al2O3‐cBN‐hBN self‐lubricating ceramics were synthesized by using a high‐pressure sintering method. The mapping relationships between sintering thermodynamic conditions, component content, and mechanical properties were established using the response surface method. The main factors influencing the mechanical properties are clarified. The formation mechanism of the excellent mechanical properties is explained. It is found that the undesired phase transformation from cBN to soft hBN can be effectively inhibited by using a low‐temperature and high‐pressure sintering process. Sintering temperatures improve the relative densities and elastic modulus of self‐lubricating ceramic but have little effect on the hardness and fracture toughness. cBN content is the main factor affecting the mechanical properties of the composites. The microcracks developed during the high‐pressure sintering process contribute to the fracture toughness of the composites. [ABSTRACT FROM AUTHOR]

The article presents the results of comparative tests on the wear resistance of composite materials (CM) sintered at high pressures and temperatures based on impact diamond (diamond-lonsdaleite abrasive — DLA) when processing silicon carbide (SiC). To assess the CM performance based on impact diamonds, a method has been developed for determining the wear resistance, based on the determination of the CM specific productivity. It is shown that for CMs based on impact diamond, it is expedient to use SiC as a binder. For CMs based on impact diamond with an additive of 40 vol.% SiC, specific productivity when machining a silicon carbide wheel is 25–30 % higher than for compositions containing dense BN phases — wBN and cBN. The decrease in the specific productivity of CM “impact diamond — cBN” relative to CM “impact diamond — SiC” is determined by the higher dispersion of crystals of dense BN phases in comparison with SiC, which generally impairs the abrasive ability of the material. In this case, the addition of a coarse fraction of impact diamond 100/63 μm to the charge composition does not lead to an increase in the specific productivity of the abrasive element as compared to CM based on DLA with a particle size of less than 40 μm. Preliminary mechanical activation of the initial charge also reduces the CM abrasive ability due to the formation of a highly dispersed structure of the material.

The performance of cutting tool materials (CTMs) influences the quality and lifetime of the parts produced using these tools. Unexpected fracturing or other failures of the tools lead to defects of the parts, which accelerates material fatigue and fracture processes. For the purpose of Industry 4.0 and future generations of factories, it is important to enable in-situ monitoring of cutting processes while hyperspectral imaging can serve as a powerful tool. Cubic boron nitride (cBN) has extreme hardness and can provide improved wear resistance if mixed with other CTMs. Moreover, such materials can be used without cutting fluids, which helps to mitigate health risks in the workplace. The aim of the current work was to understand how well the current hyperspectral imaging technologies can track the changes in the performance of CTMs with the addition of cBN. This paper presents the results of multiple in-situ (obtained during cutting with a real lathe) and static (before or after cutting) tests performed with hyperspectral camera. The wear rate of CTMs and the roughness of workpieces were measured with the help of a scanning electron microscope and a 3D optical profiler respectively. The effect of cBN content and the effect of TiN or ZrO2 additives on the performance of alumina-based CTMs produced by spark plasma sintering technique is presented.

This paper is focused on the issue of preparing the cutting edge microgeometry of cutting inserts made of cubic boron nitride (CBN). The aim of this research was to investigate the possibilities of rotary ultrasonic machining (RUM) for preparing asymmetric cutting edge microgeometries of various shapes (chamfers, circular, and elliptical rounding and their combinations) on a CBN cutting tool. In this article, a new type of advanced cutting edge preparation method is presented. CBN is relatively resistant to the most often used (abrasive) methods of cutting-edge preparation, due to its very high hardness (which is a prerequisite property for machining difficult-to-cut materials). Such hard materials could be processed using advanced manufacturing methods, and rotary ultrasonic machining (RUM) is one such method. Experiments have shown that RUM can be used for machining CBN. However, high hardness is not the only challenge here. For cutting edge preparation, it is necessary to achieve an adequate accuracy of size and dimensions. The presented paper analyzes the suitability of the RUM process for processing CBN inserts. The results of the experiment showed that this method can be used for preparing asymmetric cutting edge microgeometries with various shapes. [ABSTRACT FROM AUTHOR]

Tungsten carbide (WC) with different amounts of Cubic boron nitride (cBN) were synthesized by High Pressure-High Temperature (HPHT) method. The mapping correlation between thermodynamic condition, cBN addition, and microstructure, mechanical properties of WC–cBN composites was established and analyzed by response surface methodology. The main factors affecting the properties of composites were identified by ANOVA. The optimum thermodynamic condition was calculated. It was found that a minor phase transformation of cBN into the low-hardness hBN occurred at a temperature of 1300 °C and intensified at 1500 °C. The homogeneously dispersed cBN particles in the WC matrix promoted an improvement of hardness and fracture toughness, but the phase transition of cBN and its truss effect can dramatically reduce the mechanical properties. The Vickers hardness and fracture toughness of the well-sintered WC-cBN bulks reached a high value of 34 GPa and 13.6 MPa·m1/2, which are improved by 17% and 52% respectively compared with the pure WC samples sintered under similar high-pressure level. [ABSTRACT FROM AUTHOR]

Kevlar fiber and brass wire mesh reinforced with cubic boron nitride (CBN) particle‐toughened epoxy composites are investigated in this study. This study aims to determine the hybrid composite's mechanical and drop load impact behavior, as well as the effect of surface treatment on the lamina delamination resistance and load bearing phenomenon. The composite laminates were fabricated by hand layup process and characterized according to ASTM standards. The tensile, flexural, Izod impact, ILSS, and hardness testing results shows that adding 35 vol% reinforcements and 3.0 vol% CBN particles indicates the greatest research findings. However, when the stacking sequences B/K/K/B and K/B/B/K were modified from B/K/B/K, these values reduced. The EO2 composite shows improved results in mechanical and drop load impact behavior together with Kevlar fiber and brass wire mesh of alternating staking sequences with 3.0 vol% CBN particles. It is clear that B/K/B/K stacking sequence shows the highest mechanical properties and drop load impact behavior while, B/K/K/B shows lowest values. This hybrid composite with higher mechanical qualities and impact energy absorption might be used in defense armors, aerospace, structural, automobile, and household equipment manufacturing applications. [ABSTRACT FROM AUTHOR]

Polycrystalline boron nitride cutting tools are widely used for hard-part steel turning due to their high wear resistance and long durability, however microstructurally different boron nitride composites are suited for different machining applications. For example, low cBN content grades (cBN<50%) are used in continuous and lightly interrupted cutting of automotive steels and in the machining of valve seat alloys; while high cBN content grades (cBN>85%) are designed to provide excellent abrasion and chip resistance and therefore are suitable for interrupted machining of grey and hard cast irons, hardened steel milling and in machining valve seat alloys where a longer tool life is required. In this paper, using a nanosecond fibre laser (1064-nm wavelength), surface engineering of polycrystalline of two microstructurally different boron nitride materials (50% and 90% cBN content) is proposed to functionalise the mechanical properties and enable to extend the applicability of a specific grade to a variety of machining applications. The materials' response to different fluences, feed speeds and pulse durations was investigated and characterised through a combination of 3D white light interferometry, scanning electron microscopy (SEM) and micro-hardness measurements. 3D metrological data (Sa, Spk, Sku and Sq) of the samples were measured prior and post-process to provide an indication of the change in wear properties. Fractures between hard grains and binder and reduced surface integrity were highlighted by SEM analyses due to thermal stress caused by a difference in thermodynamic properties between grains and binder. Increased frequency and energy density caused local heating corroborated by larger Sa, Spk and Sq values but lower Sku values. Micro-hardness measurements revealed up to 20% increased hardness and 10% decreased root mean square height (Sq) with reduced feed speed and energy density per pulse. Improvements to the hardness and reductions in the surface roughness of both PCBN grades were observed, suggesting that the use of laser surface engineering could lead to improvements in performance in application in the automotive industry beyond the conventional application for the specific grade. [ABSTRACT FROM AUTHOR]

The examination on grinding single crystal silicon slice using newly developed CNT (carbon nanotubes) reinforced micro grinding wheel were performed. A specially designed four-legged vacuum chuck was fabricated to hold the workpiece and ground the sliced silicon surface using with and without CNT reinforced micro grinding wheel in which the diameter is 50.65 mm. In order to understand the stability of the fixture, a vibrational analysis was performed, which was supported by a vibrational sensor. The diameters of a single crystal silicon slice are 25 mm. The vacuum chuck has mounted silicon slice was grinding using CBN (Cubic boron nitride) and CNT infused CBN micro-wheel in dry condition. After grinding, the surface quality was analyzed, it was found that the CNT composite micro grinding wheel can be used to precisely ground brittle materials like single crystal silicon. It was noticed that the slice ground by CNT infused micro wheel had a smooth surface with minor waviness, which is based on wheel speed, feed rate and depth of cut and the stability of the fixture. The result shows that the surface roughness of the silicon slice grounded with CBN (Cubic boron nitride) is around Ra 1.1464–1.8631 μm and CNT infused CBN micro-wheel is about Ra 0.6154 μm when other settings are not changed. The influence of CNT in the silicon samples was characterized through surface roughness measurements, scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM) studies. It was found that the stresses developed in the material and the assembly was within the permissible limits, and the surface quality of grinding with cnt infused CBN micro-grinding wheel is better than without CNT. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (CBN), with a hardness second only to diamond and an excellent chemical stability, is used to replace the role of diamond and machine precision/ultra-precision components in ferrous materials. However, the wear mechanisms of CBN tools and their wear-induced effects on machining system vibration seriously affect the machined surface quality. Therefore, this research focus on the wear characteristics of CBN tools in machining of NAK80. Based on the wear characteristics, the change in surface morphology and finish of the machined surface with tool wear was investigated. Meanwhile, the transformation of chip morphology at different wear stages was observed. Also, the effect of tool wear on the machining system vibration is analyzed by Butterworth filtering and Fourier transforming the cutting force signal. Research results show that the wear mechanisms of CBN cutting NAK80 are abrasive wear, oxidative wear and diffusive wear. Further, when the width of the flank wear of the CBN tool reaches 53 μm it causes multimodal vibration of the machining system, resulting in chattering patterns on the machined surface. As the width of the flank wear increased from 56.64 μm to 70.80 μm, the vibration frequency increased by 13.3 %. However, by reducing the feed rate from 5 μm/rev to 2 μm/rev, the vibration frequency can be reduced by 66.8 %. This study provides theoretical help in the research of wear of CBN cutting NAK80. • T ool wear in CBN machining NAK80 is a combination of mechanical and chemical wear. • CBN tool lose their machinability and causes machining system vibration when the flank wear width exceeds 53 μm. • CBN tool wear causes energy storage and release of machining system and further surface chattering patterns. • The chip morphology tends to be scalloped jagged as the CBN tool wear progresses. • Vibration frequency increases with tool wear progress, and reducing feed rate can suppress the vibration. [ABSTRACT FROM AUTHOR]

Trace amounts of Mg deposited on a diamond (100) substrate surface facilitate the growth of cubic boron nitride (c‐BN) by ion beam‐assisted molecular beam epitaxy. Fourier transform infrared spectroscopy indicates that films grown with Mg are cubic, while those without Mg are either hexagonal BN or lacking measurable cubic or hexagonal signatures. Initiating the growth with 0.005 monolayer equivalent of Mg is sufficient to yield epitaxial films with >99% c‐BN. Reflection high energy electron diffraction, electron energy loss spectroscopy, and X‐Ray photoelectron spectroscopy indicate the surface of the film to be sp2‐bonded BN, consistent with the results of other groups. High‐resolution scanning transmission electron microscopy reveals c‐BN with a high density of stacking faults and twinning. A model is proposed by which Mg locally diminishes the energy barrier to dissociation of the as‐deposited sp2‐bonded BN, facilitating the nucleation of c‐BN. [ABSTRACT FROM AUTHOR]

The nickel (Ni) coatings without and with embedded (5–7 vol. %) cubic boron nitride (c-BN) nanoparticles (10 nm in diameter) were deposited on carbon steel substrate by an electroless plating process. Coatings were tested in as-deposited and heat-treated (heating at 300 °C for 6 h) conditions. Coating structure characterisation was performed, as well as hardness and roughness measurements. Friction properties were tested in dry and in water (seawater) lubricated contact conditions, with bronze as a counter-body material. Both static and kinetic coefficients of friction were measured for two different surface texture preparations (initial and working). The first surface texture simulated the running-in condition, and the second surface texture represented the steady-state conditions. The enhancement of the abrasive and erosive wear resistance of heat-treated electroless Ni coatings with embedded c-BN nanoparticles was already proved in our previous studies. This study aims to investigate those influences on friction properties of electroless Ni coatings in different sliding conditions. The results show that the coefficients of friction did not differ too much between the coatings and that the surface roughness and presence of seawater had a much stronger influence. [ABSTRACT FROM AUTHOR]

Extending the use of a component without compromising its intended functionality is the neatest approach to enhance sustainability. From this perspective, limiting the working life of a cutting tool based merely on the blunting of its cutting edge to a specific value is highly questionable. The very question that serves as the motivation for this work is, "why should tool life criterion be based on the shape of the tool when all that matters for business is the quality of the part being machined?". This work puts forward a tool life criterion based on the surface quality of the machined part. The proof of the concept is provided by a series of face-turning experiments performed on a commonly used alloy steel using the following cutting inserts in dry conditions: (1) uncoated carbide; (2) coated carbide; and (3) cubic boron nitride (CBN). It is found that different combinations of tooling and cutting parameters lead to entirely different values of surface roughness at the same level of flank wear, thus raising the possibility of extending the working life of the tools. Overall, the CBN inserts yielded the longest tool life values, especially at high levels of cutting speed. Being more economical in respect of acquisition cost than the CBN inserts and more effective than the uncoated carbide inserts regarding tool life, the coated carbide inserts came out as the most sustainable tooling option. Finally, it is concluded that a tool life criterion based on work surface roughness can yield longer tool life values and make the machining process more sustainable. For the experimental work reported herein, the surface-quality based tool life criterion yielded on average 23% longer tool life. The presented work is novel as it presents a new approach to extend the working life of cutting tools without compromising the other sustainability measures. The outcomes are expected to find applicability in all sectors of the metal cutting industry, which are striving for elongations in tool life and improvements in work surface quality. [ABSTRACT FROM AUTHOR]

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As the Ⅲ-Ⅴ binary compound with the face-centered cubic structure of sphalerite, cubic boron nitride ( c-BN) exhibits the largest band gap as one of the typical third-generation semiconductors, as well as other excellent properties including high thermal conductivity, high hardness, high-temperature oxidation resistance, chemical stability, wide range of light transmission wavelength, and can be both doped into p-type or n-type. It can be not only widely used as a superhard materials in the processing fields of various industries, but also has potential applications value as extreme electronics materials in high-power semiconductor and optoelectronic devices, making it suitable for extreme environments such as high temperature, high power, high pressure, high frequency and strong radiation. This article reviews the development of c-BN crystal preparation and epitaxial growth of c-BN thin films in recent years, focusing on the progress of growth technology and the improvement of crystal quality, as well as their mechanical, optical and electrical properties. Finally, the paper summarizes the content of the paper and prospects the challenges of c-BN application. [ABSTRACT FROM AUTHOR]

Al2O3-based self-lubricating ceramics are cutting tool materials that meet the extreme working conditions of dry cutting. However, due to the soft lubricating components, the mechanical properties of composites are dramatically reduced. In this paper, Al2O3-cBN-hBN self-lubricating material was designed. High density, fine grain ceramics were synthesized by high-pressure technology. The influence of thermodynamic condition, cBN/hBN addition on mechanical and thermal properties of sintered composites was analyzed. Friction and wear tests were carried out. It is found that the addition of cBN particles can significantly improve the mechanical and thermal properties of the composites. However, the truss effect caused by excessive volume fraction of cBN can reduce the pressure transfer efficiency, and then affect the properties of sintered composites. The different hBN content can change the wear mechanism of the composites. The release efficiency of hBN particles in composites was enhanced due to the large modulus difference between cBN and hBN. The well-sintered Al2O3-cBN-hBN bulks present an excellent mechanical property. The hardness of the composites is improved at least by 54% compared with the traditional self-lubricating material on the premise of ensuring fracture toughness and lubrication performance.

We analyze the real and imaginary parts of cBN in a broad wavelength range both 0.5-1.0 µm and 1.36-10 µm respectively, and use both Fresnel theory and Meep software package to calculate the transmittance and reflectance. The theoretical and numerical results show that the transmision and reflection on the interfaces mentioned above have an abnormal phenomenon, and the physical mechanism is analyzed. Between 0.5 μm and 1 μm, the cBN film is transparent with the transmissivity equal to the order of 1.0. When the light wavelength is in the range of 4-9 μm, the structures made of cBN and Si, such as cBN film, cBN-Si double layer film and multiple layer film, have the same optical characteristic with the highest reflectivity and lower absorptivity and zero transmissivity. These findings can be used in the structure design of the optoelectronic devices, such as the optical bandpass filter, the optical bandstop filter, the optical attenuator, the photodetector, and the solar cell.

Cubic boron nitride (c‐BN) is a potential candidate material for electronic and optoelectronic devices under extreme conditions, while the difficulty in conventional doping severely hinders its applications. Herein, by first‐principles calculation, an efficient p‐type doping on the c‐BN surface (areal hole density of 8.82 × 1013 cm−2 and hole mobility of 826 cm2 V−1 s−1 at room temperature) is realized by the surface charge transfer mechanism with the MoO3 molecule having a high electron affinity as the dopant. The MoO3 molecule draws electrons from the c‐BN, making the hole accumulation on the c‐BN surface. The areal hole density of c‐BN enhances with the increase of MoO3 molecule density and reaches the maximum (1.24 × 1014 cm−2) with MoO3 monolayer adsorption. The optical absorption coefficient significantly increases in the infrared and visible regions. The superior p‐type doping for c‐BN is also achieved by adsorbing transistor metal oxides with the high electron affinity values (such as ReO3, CrO3, WO3, and V2O5). This study opens a novel avenue for promoting c‐BN applied in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (CBN) has high hardness and superior thermal conductivity, and it was used to fabricate an oscillating heat pipe abrasive wheel (OHPGW) for the eco-benign grinding of hard-to-machine materials. Furthermore, the wear behavior of the CBN grains and the related lifecycle of the OHPGW are important. In this study, a comparative analysis was conducted to reveal the wear behavior of CBN grains on OHPGWs and conventional wheels. Under the enhanced heat transfer effect of the OHPGW, the CBN grain wear behavior, development of the CBN protrusion heights, and the ground surface quality were investigated. The CBN grains on the abrasive wheel experience initial, stable, and fast wear periods in conditions of attrition, micro-fracture, and macro-fracture. Owing to the low grinding heat and temperature acting on the OHPGW, the CBN grains mostly undergo attrition during the stable period, while CBN grains on the conventional wheel mainly undergo micro and macro-fractures. As the wear of the CBN grains progressed, the average protrusion height of the CBN grains decreased. The scattering of the protrusion height distribution decreased at first and then increased when entering the fast wear period. Consequently, the surface topography and roughness initially improved and then deteriorated with the development of the protrusion height distribution of the CBN grains. [ABSTRACT FROM AUTHOR]

This study attempt to investigate microstructural, thermomechanical and tribological properties of low-temperature sintered cBN and Ni-coated cBN reinforced bearing steel composites. Ultrasonic probe sonication and spark plasma sintering (SPS) at 900 and 1000 °C were utilized for the dispersion and consolidation, respectively. Findings show that up to 30 wt.% addition of cBN particles, no significant effect on the thermal properties, for the selected sintering temperatures. However, the introduction of Ni-coated cBN reinforcement caused a considerable impact on thermomechanical properties. The developed composites exhibited improved tribological properties as compared to the unreinforced bearing steel. Similarly, samples sintered at a higher temperature of 1000 °C possessed enhanced wear resistance in comparison to samples sintered at 900 °C. Furthermore, Ni-coated cBN reinforced samples exhibited superior wear resistance. However, more than 10wt.% of Ni-coated cBN reinforcement led to material loss, whereby some of the Ni melted out from the consolidated composite during the sintering process.

High pressure and high temperature experiments with a Hall belt apparatus of cathodic arc deposited Ti0.63Al0.37N and Ti0.37Al0.63N on polycrystalline cubic BN substrate reveal a strong influence of pressure on the decomposition rate of TiAlN. The pressure induces enhanced phase stability while keeping the interfaces between coatings and the substrates intact. Hardness measurements of the as-deposited coatings and after high-pressure high-temperature treatment show that the hardness after treatment of Ti0.63Al0.37N at 5.35 GPa, 1300 °C and after 66 min drops from 29.6 to 27.8 GPa, because after this treatment this sample contains cubic TiN and hexagonal AlN. This drop is much smaller than if the coatings are just heat treated at 1300 °C and suggests that an enhancement of TiAlN-coatings on cubic BN cuttings tools can be achieved by increasing the pressure/stress during cutting. For Ti0.37Al0.63N treated at 5.35 GPa, 1300 °C and after 66 min the hardness drops from 36.1 to 28.6 GPa, which means that the coating has first decomposed through spinodal decomposition and one of products of this decomposition has further phase transformed and the final products are cubic TiN and hexagonal AlN.

• This article systematically investigated the pressure and temperature effects on recrystallization behavior of cBN grains. • The results show that the recrystallization temperature of cBN under 8 GPa is approximately 1650 °C and increases by approximately 100 °C with every 2 GPa increase in pressure. • Once grain recrystallization starts, the strengthening effects of grain refinement and defect structure are greatly weakened. • This work is helpful to understand the sintering mechanism and control the microstructure and mechanical properties of sintered polycrystalline cBN compacts. • In addition, the melting curve for cBN under high pressure is inferred according to the empirical relationship between recrystallization temperature and melting temperature, and the phase diagram for boron nitride is revised based on this new melting curve. The recrystallization behaviour of micron-sized cubic boron nitride (cBN) was studied by analysing the grain size and morphology of samples treated at 8−16 GPa/1500–2200 °C. The results show that the recrystallization temperature of cBN under a pressure of 8 GPa is approximately 1650 °C and increases by approximately 100 °C with every 2 GPa increase in pressure. Once grain recrystallization starts, the grains grow abnormally quickly as the temperature rises, and the strengthening effects of grain refinement and defect structure are greatly weakened. The recrystallization behaviour of cBN at high pressure is helpful to understand the sintering mechanism and control the microstructure and mechanical properties of sintered polycrystalline cBN compacts. In addition, the melting curve for cBN under high pressure is inferred according to the empirical relationship between recrystallization temperature and melting temperature, and the phase diagram for boron nitride is revised based on this new melting curve. [ABSTRACT FROM AUTHOR]

This article deals primarily with the problem of determining the cutting force when machining hardened steels. For this study, the steel used was 100 Cr6, number 1.3505. The secondary aspects of the study focused on the evaluation of the surface quality of machined samples and the recommendation of cutting conditions. A wide variety of components are used in engineering, the final heat treatment of which is hardening. These components are usually critical in a particular product. The quality of these components determines the correct functioning of the entire body of technical equipment, and ultimately, its service life. In our study, these are the core parts of thrust bearings, specifically the rolling elements. The subject of this experiment involves machining these components in the hardened state with cubic boron nitride tools and the continuous measurement of the cutting force using a dynamometer. The machining is carried out on a conventional lathe. A total of 12 combinations of cutting conditions were set. Specifically, for three cutting speeds of 130, 155 and 180 m·min−1, the feed rates of 0.05 and 0.1 mm·rev−1 and the cutting widths of 0.2 and 0.35 mm, were evaluated The evaluation assessed the surface quality by both touch and non-touch methods. A structural equation with the appropriate constants and exponents was then constructed from the data obtained using the dynamometer. The experiment confirmed the potential of achieving a value of the average arithmetic profile deviation Ra in the range of 0.3–0.4 when turning hardened steels with cubic boron nitride.

In the mechanical, automobile, aerospace, and construction industries, Ti and steel are the mostly commercial materials be used. But the poor hardness, wear, and corrosion resistance limit their applications. In this study, we presented a composite material that consists of thermal-sprayed titanium (Ti) layer on AISI 1020 steel. Then we added different concentrations of c-BN to the electrolyte in the MAO process to enhance the wear resistance and corrosion resistance. The operating parameters of MAO were set to 35A/dm2 current density, 450V voltage and 10 minutes operating time. The concentration of c-BN added to the electrolytes were 0.1 g L-1, 0.3 g L-1, 0.5 g L-1, 0.7 g L-1, 0.9 g L-1, and denoted as Ti/MAO-BN1, Ti/MAO-BN3, Ti/MAO-BN5, Ti/MAO-BN7, Ti/MAO-BN9, respectively. To determine the properties of the composite coating, measurements of coating thickness, surface roughness, microstructure, hardness, XRD analysis, EDS observations were performed. Then potentiodynamic polarization test and a ball-on-disc wear test were used to determine the corrosion resistance and wear resistance. All the results indicated that all Ti/MAO contained c-BN (Ti/MAO-BN) have higher hardness, lower surface roughness, and thicker coatings thickness than that of Ti/MAO-free (Ti/MAO-F). In the corrosion resistance, Ti/MAO-BN was at least about 64% better than Ti/MAO-F, with Ti/MAO-BN9 being about 5 times better. In the wear resistance, Ti/MAO-BN reduces the wear volume at least about 59% compared to Ti/MAO-F, with Ti/MAO-BN9 reducing the wear volume by about 70%. [ABSTRACT FROM AUTHOR]

• A novel route is demonstrated to synthesize superhard bulk nanocrystalline cubic boron nitride. • A route that combines emulsion detonation and high pressure high temperature transformation-assisted consolidation. • Design insights on how to refine grains while enhancing densification to synthesize bulk nanocrystalline materials. Synthesizing bulk nanocrystalline materials is challenging since grain growth should be suppressed whereas densification promoted. Here, we demonstrate a novel route to synthesize superhard bulk nanocrystalline cubic boron nitride (cBN), which combines the use of emulsion detonation and high-pressure high-temperature transformation-assisted consolidation. The emulsion detonation process activates BN to possess unique structure and chemistry, i.e. wurtzitic BN nanograins in hexagonal BN matrix with enhanced structural disordering and oxygen impurity, a combination that enhances the nucleation rate of cBN and its densification leading to the formation of bulk nanocrystalline cBN at reduced conditions. The cBN, synthesized at 7.5 GPa and 1800 °C, displayed Vickers hardness values of 50−62 GPa for 5−20 N loads. The findings in the study suggest a feasible solution to synthesize bulk nanocrystalline cBN in a more scalable way, while also providing design insights on how to refine grain growth while enhancing densification to synthesize bulk nanocrystalline materials. [ABSTRACT FROM AUTHOR]

Abstract A series of high solid content (30 wt%) epoxy resin (EP) composite coatings reinforced with differently sized cubic boron nitride (CBN) particles were fabricated successfully on 304L stainless steel. Polydopamine (PDA) was used to improve the dispersibility of CBN particles in EP. The structural and morphological features of the CBN particles and the composite coatings were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Moreover, a UMT-3 tribometer and surface profiler were used to investigate the tribological behaviors of the as-prepared composite coatings. Electrochemical impedance spectroscopy (EIS) and Tafel analysis were used to investigate the coatings’ anti-corrosion performance. The results demonstrated that the CBN fillers could effectively enhance the tribological and anti-corrosion properties of the EP composite coatings. In addition, when the additive proportion of the microsized (5 μm) and nanosized (550 nm) CBN particles was 1:1, the tribological property of the EP composite coatings was optimal for dry sliding, which was attributed to the load carrying capability of the microsized CBN particles and the toughening effect of the nanosized CBN particles. However, when the additive proportion of the microsized and nanosized CBN particles was 2:1, the tribology and corrosion resistance performance were optimal in seawater conditions. We ascribed this to the load-carrying capacity of the microparticles, which played a more important role under the seawater lubrication condition, and the more compact structure, which improved the electrolyte barrier ability for the composite coatings.

This paper is focused on the issue of preparing the cutting edge microgeometry of cutting inserts made of cubic boron nitride (CBN). The aim of this research was to investigate the possibilities of rotary ultrasonic machining (RUM) for preparing asymmetric cutting edge microgeometries of various shapes (chamfers, circular, and elliptical rounding and their combinations) on a CBN cutting tool. In this article, a new type of advanced cutting edge preparation method is presented. CBN is relatively resistant to the most often used (abrasive) methods of cutting-edge preparation, due to its very high hardness (which is a prerequisite property for machining difficult-to-cut materials). Such hard materials could be processed using advanced manufacturing methods, and rotary ultrasonic machining (RUM) is one such method. Experiments have shown that RUM can be used for machining CBN. However, high hardness is not the only challenge here. For cutting edge preparation, it is necessary to achieve an adequate accuracy of size and dimensions. The presented paper analyzes the suitability of the RUM process for processing CBN inserts. The results of the experiment showed that this method can be used for preparing asymmetric cutting edge microgeometries with various shapes.