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This letter reports the design, simulation, optimization, and optical characterization of an electro-optical SiO2-calcium barium niobate (CBN)-MgO rib waveguide structure. To achieve the single mode and low loss operation, the proposed rib waveguide structure is simulated and optimized with respect to CBN thin film thickness, etching depth, and rib width. Propagating optical mode profile of the waveguide is simulated using a beam propagation method solver. To verify the design and simulation, CBN thin film is coated on MgO substrate using a pulsed laser deposition technique, and SiO2-CBN-MgO is fabricated with various CBN thicknesses and rib widths. A smooth and nearly vertical etching of rib side wall enables the fabrication of high quality rib waveguides. The waveguides are characterized and measured wave profiles are compared with simulated results. It is found that the guided modes are well confined within the rib and extended through the core. An excellent agreement between simulations and measurements is observed, thereby validating the design method. [ABSTRACT FROM PUBLISHER]

The hardness characteristic of nano-polycrystalline cBN synthesized by direct conversion sintering was thoroughly investigated using Vickers and Knoop indenters. It was found that nano-polycrystals consisting of smaller cBN grains increase the elastic recovery of indentations during unloading of the indenters and the diagonal of Vickers indentations and the minor diagonal of Knoop indentations significantly decrease in length. Thus, if a Vickers indenter is used, the apparent hardness value increases, making it impossible to perform an accurate evaluation, e.g. incorrect Vickers hardness values in excess of 80 GPa were obtained from nano-polycrystalline cBN with a grain size of 50 nm or less. On the other hand, it was verified that a Knoop indenter ensures an accurate hardness evaluation even if the constituent grains are fine because its major diagonal length which is used for measurement is less susceptible to elastic recovery. In an accurate evaluation of the hardness of different types of nano-polycrystalline cBN using a Knoop indenter, the hardness of each type of cBN was around 45 GPa, and there was no clear Hall-Petch relationship between hardness and grain size without a slight bell-like correlation. These results suggest that reported hardness values higher than 80 GPa of similar nano-polycrystalline cBN evaluated using a Vickers indenter are incorrect values caused by elastic recovery occurring at the indentation. [ABSTRACT FROM AUTHOR]

Abstract: The present work concerns an experimental study of hard turning of AISI 52100 bearing steel, with CBN tool. The combined effects of process parameters (cutting speed, feed rate, depth of cut and cutting time) on performance characteristics (tool wear, surface roughness, cutting forces and metal volume removed) are investigated using ANOVA analysis. The relationship between process parameters and performance characteristics through the response surface methodology (RSM) are modeled. Moreover, Grey-Taguchi method, composite desirability function and genetic algorithm are used as multi-objective optimization approaches to find the process parameters values that optimize simultaneously the performance characteristics. The results show that the cutting speed exhibits maximum influence on abrasive tool wear. The depth of cut affects strongly the cutting forces; however, it has a negligible influence on surface roughness. The cutting time has a considerable effect on all performance characteristics. Though the optimization approaches predicted near similar results, the GA technique seems to be the most advantageous approach. Finally, the proposed experimental and integrated approaches bring reliable methodologies to model, to optimize and to improve the hard turning process. They can be extended efficiently to study other machining processes. [Copyright &y& Elsevier]

Abstract: This paper presents an experimental investigation on micromilling of fully sintered Zirconia ceramics by means of advanced cutting tools, including cBN and diamond coated mills. Zirconium oxide is selected because of its high hardness, resistance to wear, heat and chemicals. Two-flute end mills of nominal diameter 1mm and negative rake angle were used. The effect of the coating and tool material, along with the cutting parameters, were investigated by means of a one-factor variation experimental design; and the responses of interest, including tool wear and sample surface quality, were monitored over the machining time. The worn tools and the machined surfaces were also analyzed on a SEM to investigate the type of material removal mechanisms (MRM). The diamond coated tools provide the best performance in terms of life time, however delamination of the diamond coating followed by wear of the underlying hardmetal is identified as the prevailing tool wear mechanism. A ductile type of material removal mechanism could be observed, inducing an achievable surface roughness below 60nm. On the contrary, cBN tools exhibited fast breakage. A combined ductile-brittle material removal mechanism occurs, resulting in a surface roughness around 300nm. [Copyright &y& Elsevier]

Using hBN and pBN as starting materials, various types of binderless polycrystalline cBN (BL-PcBN) were synthesized in the pressure range of 8–20GPa and temperature range of 1300–2400°C, and their mechanical properties were evaluated. In the synthesis pressure range of 10GPa and higher, the hardness of BL-PcBN showed a correlation not with the synthesis pressure, but with the synthesis temperature. Binderless polycrystalline cBN synthesized at about 2200°C exhibited the highest mechanical properties, for both starting materials. Specifically, BL-PcBN(h) (100–300nm grain size) synthesized from hBN at 10GPa and 2200°C showed a hardness of 45GPa, transverse rupture strength of 1.6GPa. In contrast, BL-PcBN(p) synthesized from pBN at the same temperature had finer grain size (50–100nm) and exhibited the same level of hardness but lower strength properties (transverse rupture strength of approx. 1.3GPa) than BL-PcBN(h). Consequently, the material that exhibited the best mechanical properties was BL-PcBN(h) synthesized at 10GPa and 2200°C. A prototype micro ball end mill made of this material was examined in a mirror-like (polished-like) finishing test using high-strength hardened steel. This ball end mill achieved a fine finishing surface with a surface roughness (Ra) of 20nm or better. The test revealed the high potential of this material for use as a high-precision cutting tool for high strength ferrous materials. [ABSTRACT FROM AUTHOR]

The paper presents the results of comparative study of performance of cutting tools made of ceramic-bound, binderless cBN, and wBN-cBN tool materials. The tool performance was assessed by tool wear-resistance, values of cutting forces, parameters of machined surface quality, and the state of sub-surface layer generated in continuous turning of hardened cold work tool steel. The tests were carried out under conditions of high speed machining ( v = 120-180 m/min) both with and without a coolant. The best tool performance by the above-mentioned criteria is provided by a low-cBN material with ceramic binder. [ABSTRACT FROM AUTHOR]

Cannabis is the most widely used illicit substance globally, with an estimated annual prevalence in 2010 of 2.6-5.0% of the adult population. Concerns have been expressed about increases in the potency of cannabis products. A high tetrahydrocannabinol (THC) content can increase anxiety, depression, and psychotic symptoms, and can increase the risk of dependence and adverse effects on the respiratory and cardiovascular systems in regular users. The aim of this study was to report statistical data about the potency of cannabis products seized in the north-east of Italy, in a geographical area centred in Venice and extending for more than 10 000 km2 with a population of more than two million, by investigating the variability observed in THC levels of about 4000 samples of cannabis products analyzed over the period 2010-2012. Overall median THC content showed an increasing trend over the study period from about 6.0% to 8.1% (6.2-8.9% for cannabis resin, 5.1-7.6% for herbal cannabis). The variation in the THC content of individual samples was very large, ranging from 0.3% to 31% for cannabis resin and from 0.1 to 19% for herbal cannabis. Median CBN:THC ratios showed a slightly decreasing trend over the study period, from 0.09 (2010) to 0.03 (2012), suggesting an increasing freshness of submitted materials. Median CBD:THC ratios also showed a decreasing trend over the study from about 0.52 (2010) to 0.18 (2012), likely due to the increase in submissions of materials from indoor and domestic cultivation with improved breeding methods. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Epidermal growth factor receptor (EGFR) is a member of the ErbB family of proteins and are involved in downstream signal transduction, plays prominent roles in cell growth regulation, proliferation, and the differentiation of many cell types. They are correlated with the stage and severity of cancer. Therefore, EGFRs are targeted proteins for the design of new drugs to treat cancers that overexpress these proteins. Currently, several bioactive natural extracts are being studied for therapeutic purposes. Cannabis has been reported in many studies to have beneficial medicinal effects, such as anti-inflammatory, analgesic, antibacterial, and anti-inflammatory effects, and antitumor activity. However, it is unclear whether cannabinoids reduce intracellular signaling by inhibiting tyrosine kinase phosphorylation. In this study, cannabinoids (CBD, CBG, and CBN) were simulated for binding to the EGFR-intracellular domain to evaluate the binding energy and binding mode based on molecular docking simulation. The results showed that the binding site was almost always located at the kinase active site. In addition, the compounds were tested for binding affinity and demonstrated their ability to inhibit kinase enzymes. Furthermore, the compounds potently inhibited cellular survival and apoptosis induction in either of the EGFR-overexpressing cell lines., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Authors.)

[Display omitted] • The tip energy of V-shaped grinding wheel was lower, which could be used as an evaluation index of truing state of V-shaped grinding wheel. • Larger grinding wheel speed n would bring higher energy value and more stable energy distribution, while truing depth h would not affect the value and stability of energy. • The angle of V-shaped grinding wheel could reach 90.15° (deviation 0.02°), the bottom fillet radius was 53 μm (less than 100 μm). The laser truing could improve grinding quality and efficiency on the premise of ensuring V-shaped profile, and could be a good substitute for mechanical truing. The machining difficulty has limited the further application of ultra-hard materials. For V-shaped coarse-grained electroplated cubic boron nitride (CBN) grinding wheel, a precise and efficient pulse laser truing method was proposed. Firstly, a theoretical model of the pulse laser truing process was established in order to optimize the laser truing energy distribution. Secondly, the effects of truing depth, grinding wheel speed, laser power and truing time were analyzed. Finally, the grinding performance of laser trued wheels were evaluated. The results showed that larger grinding wheel speed n would bring higher energy value and more stable energy distribution, truing depth h would not affect the value and stability of energy. CBN would not undergo phase transition and could bear more laser power P avg. With the increase of truing time t , the geometric precision of V-shaped grinding wheel could be improved. The angle of V-shaped grinding wheel could reach 90.15° (deviation 0.02°), the bottom fillet radius was 53 μm (less than 100 μm). The surface roughness and grinding force corresponding to laser truing were less than that of mechanical truing, the truing time required was reduced by 72%∼83%, and the corresponding tooth profile angle and bottom fillet were basically the same. [ABSTRACT FROM AUTHOR]

Cutting tools containing superhard phases enable efficient dry machining resulting in reduced human and environmental risks. In the current work, spark plasma sintered composites containing up to 20 vol% cBN in Al 2 O 3 -based matrix with an addition of 15 vol% ZrO 2 or 10 vol% TiN have been tested under dry sliding (with multiple restarting to better simulate real working conditions) and surface fatigue (with in-situ monitoring of acceleration indicating evolution of the test area) conditions. Dry sliding was carried under two configurations of "ball above sample" and "ball below sample" to study the effect of wear debris entrapment in a wear scar. The importance of a longer test duration (40 000 s, i.e. more than 10 h) during sliding of extensively polished ceramic materials with "mild" wear regime is emphasized. The reason for long running-in process with characteristic threshold is explained. The worn surfaces were studied using scanning electron microscopy, energy dispersive spectroscopy and 3D profilometry to understand the responsible wear mechanisms. The wear rates are reported in comparison to pure Al 2 O 3 ceramic. The surface fatigue test was able to identify the material (Al 2 O 3 -20cBN-15ZrO 2) that according to previous research by authors exhibits lowest wear in dry cutting conditions. [Display omitted] • ZrO 2 addition was positive for fatigue, while TiN was detrimental in all conditions. • Ball above/below configuration was used for manipulation of wear debris entrapment. • Contact zone was in-situ monitored during fatigue and performance map obtained. • Ceramics with low roughness have 5-h long running-in with threshold in COF. • Multiple restarting enabling to trace sensitivity of the tribocontact [ABSTRACT FROM AUTHOR]

Abstract: Cubic boron nitride (cBN)-metal composites were synthesized from hexagonal boron nitride (hBN) using Co–Cr–Al, Co–V–Al and Co–Cr–V–Al as infiltration solvents under high pressure and high temperature conditions (5.6GPa and 1700°C for 30min). The alloy compositions employed in the present study were (in weight percent) Co70–Cr22–Al8, Co80–V10–Al10, Co84–V6–Al10 and Co70–Cr19–V3–Al8. It was found that the size of cBN grains in the composites synthesized using Co–V–Al solvent was relatively finer compared with the ones synthesized using Co–Cr–Al. It was also confirmed that the grain growth of cBN could be suppressed by adding a small amount of V to the Co–Cr–Al solvent. We suggest that V might be used as an additive in the metal solvent during sintering of fine grains cBN compact, where the microstructure homogeneity and the cBN abnormal grain growth are the important issues. [Copyright &y& Elsevier]

Abstract: Cubic boron nitride (cBN)-metal composites were synthesized from hexagonal boron nitride (hBN) using Co–Cr–Al base alloy as infiltration solvents under high pressures and high temperatures. To control the grain size of the cBN crystals, Mo or V was used as a substitute of Cr in the base alloy. The pressure–temperature region of the cBN formation under Co–(Cr, Mo)–Al and Co–(Cr, V)–Al systems was determined at pressure between 4 and 6GPa and temperature up to 1700°C. It was confirmed that cBN was obtained at pressures above 4.4GPa and temperatures above 1290°C. The grain size of cBN synthesized using Co–(Cr, V)–Al solvent was relatively finer comparing with the ones synthesized with Co–Cr–(Mo)–Al alloy solvent. Under the Co–(Cr, V)–Al alloy solvent system where both Cr and V exist, the grain size of the synthesized cBN could be controlled by changing the composition of Cr and V in the solvent. [Copyright &y& Elsevier]

Grinding is one of the mandatory methods for fabrication of precise glass fiber reinforced plastic (GFRP) parts. In this work, grinding studies were carried out on GFRP using a cubic boron nitride (CBN) wheel. The grinding process was performed at different cutting speeds, feed rates, and depth of cuts. Grinding performance was evaluated by measuring forces and surface roughness of the ground GFRP composite laminate material. The effects of coolants in grinding the composite laminate material were investigated. Test results showed that in most cases, dry grinding achieved the greatest material removal rate and the lowest surface area roughness (Sa). Higher speed tends to produce better surface finish in dry grinding. Surface area roughness produced in wet grinding shows random and drastic variations. Surfaces ground in synthetic coolant show clean, hard, and smooth matrix, and are in general of better quality than those ground with emulsion coolant. Optical and electron microscopy was used to evaluate the grinding mechanism of GFRP laminate material. Surface profile waviness is the predominating factor contributing to surface area roughness over surface peaks and valleys. [ABSTRACT FROM AUTHOR]

Adsorption of nitrogen dioxide in three different configurations on the exterior surface of CBN is studied using density functional theory calculations. To this end, we optimized the structures of raw CBN and nine NO-CBN complexes at the B3LYP/6-31G level of theory and then calculated chemical shielding (CS) tensors at the GIAO-B3LYP/6-311G level for the optimized structures. The calculated chemical shielding isotropy (CSI), chemical shielding anisotropy (CSA), and orientation of CS tensors (Euler angles) reveal that the adsorption configurations (nitro, trans-nitrite, and cis-nitrite) have different effects on the electronic structure of CBN. Natural atomic charges based on natural population analysis (NPA) were used to justify the changes in CSI values after gas sorption. [ABSTRACT FROM AUTHOR]

Abstract: This work reports an extensive study on the etching of Calcium Barium Niobate (CBN, a novel electro-optical material), using high density plasma processes. Different plasma chemistries (inert, chlorine and fluorine plasmas) are used to etch Ca0.28Ba0.76Nb2O6 (CBN-28) thin films at pressures going from 1 to 10mTorr, bias voltages going from 0 to 600V and substrate temperatures ranging from −75 to 375°C. For all the conditions investigated, the experimental data are compared with a simple sputtering model and completed with TOF-SIMS measurements of some of the samples processed. This study shows that there is no chemical enhancement or inhibition in the case of chlorinated plasma (Cl2) regardless of the ion energy or the substrate temperature. In the case of an SF6-Ar plasma, it is shown that the observed increase of the etch yield above 150°C results from a reduced inhibition as the temperature increases, this inhibition being caused by F and F 2 species adsorption at the surface of the material. [Copyright &y& Elsevier]

Abstract: In this study, the wear mechanism of CBN inserts while face milling of aluminum-grey cast iron engine block was investigated by means of Scanning Electron Microscopy (SEM). It was shown that the thermal cracking constitutes the main wear mechanism. The Finite Element Method (FEM) was utilized to simulate the face milling under the operational condition. The flow stress properties of the aluminum-silicon alloy and grey cast iron were determined by means of inverse methodology and the milling operation was modeled separately for each material to obtain the thermally and mechanically induced stresses on the tool edge. The methodology presented in this paper can be used to find the optimum cutting condition as well as tool geometry to reduce tool wear rate. [Copyright &y& Elsevier]

Highlights: [•] THCCOOH quantification in oral fluid could eliminate passive inhalation cases. [•] CBD and CBN in oral fluid could be markers of recent consumption. [•] Sensitive THC, THCCOOH, CBD and CBN quantification in oral fluid by LC–HRMS. [•] THCCOOH LOQ was 15pg/mL, and THC, CBD and CBN LOQ was 0.5ng/mL. [ABSTRACT FROM AUTHOR]

This experimental investigation was conducted to determine the effects of cutting conditions on surface roughness and cutting forces in hard turning of X38CrMoV5-1. This steel was hardened at 50 HRC and machined with CBN tool. This is employed for the manufacture of helicopter rotor blades and forging dies. Combined effects of three cutting parameters, namely cutting speed, feed rate and depth of cut, on the six performance outputs-surface roughness parameters and cutting force components, are explored by analysis of variance (ANOVA). Optimal cutting conditions for each performance level are established. The relationship between the variables and the technological parameters is determined through the response surface methodology (RSM), using a quadratic regression model. Results show how much surface roughness is mainly influenced by feed rate and cutting speed. The depth of cut exhibits maximum influence on cutting force components as compared to the feed rate and cutting speed. [ABSTRACT FROM AUTHOR]

B-C-N film with a ∼450 nm thickness was prepared on a (100) oriented silicon wafer (4 cm × 4 cm) by unbalanced magnetron sputtering of a BC target with a unipolar pulsed DC substrate bias. At a substrate bias of −250 V, a cubic boron nitride (cBN) phase appeared in the B-C-N film when the nitrogen content was over 6.7 vol% in Ar-N reactive gases. For the B-C-N film deposited on unipolar pulsed DC biased Si substrate with Ar-16.7%N reactive gas, the content and formation behavior of the cBN phase along with the film thickness were critically dependent on the substrate position due to the difference in ion flux. In contrast to the circular central region of a substrate 2.5 cm in diameter, where cBN was nucleated and grown on hexagonal boron nitride (hBN) in a layered manner, the cBN phase was co-grown with the hBN phase and was surrounded by hBN at the circumference region of the circle. Only hBN was observed at the outer region of the circle. The microstructure of B-C-N film in which cBN is surrounded by hBN is believed to be effective in reducing residual stress developed by the nucleation of a cBN phase. [ABSTRACT FROM AUTHOR]

We present recent developments in modelling and simulation of internal traverse grinding, a high speed machining process which enables both a large material removal rate and high surface quality. We invoke a hybrid modelling framework, including a process scale model, simulations on a mesoscale capturing the proximity of a single cBN grain and an analysis framework to investigate the grinding wheel topography. Moreover, we perform experiments to verify our simulations. Focus in this context is the influence of the cutting speed variation on the grain specific heat generation. [ABSTRACT FROM AUTHOR]

Abstract: The application of minimum quantity lubrication (MQL) in grinding has emerged as an alternative for reducing the abundant flow of cutting fluids, thus achieving cleaner production. Although considered an innovative technique in grinding operations, its widespread application is hindered due primarily to the high heat generation and wheel pore clogging caused by machined chips, harming the final product quality and increasing tool wear on the machine. This study sought to improve MQL use in grinding. In addition to the conventional MQL injected at the wheel/workpiece interface, a compressed air jet was used to clean the mixture of MQL oil and machined chips from clogged wheel pores. Experiments were conducted using external cylindrical plunge grinding on AISI 4340 quenched and tempered steel, and a vitrified cubic boron nitrite (CBN) wheel. The cooling-lubrication methods employed were the conventional flood coolant application, MQL (without cleaning), and MQL with a cleaning jet directed at the wheel surface at different angles of incidence. The main goal of these experiments was to verify the viability of replacing the traditional abundant flow of cutting fluid with MQL and wheel cleaning. The analyses were conducted by measuring the following output variables of the process: workpiece surface roughness and roundness errors, diametrical wheel wear, acoustic emission generated by the process, and metallographic images of the ground surface and subsurface. Results show the positive effects of implementing the cleaning jet technique as a technological improvement of minimum quantity lubrication in grinding in order to reduce the usage of cutting fluids. The MQL technique with cleaning compressed air jet, for a specific angle of incidence (30°), proved to be extremely efficient in the improvement of the surface quality and accurate workpiece shape; it also reduced wheel wear when compared to the other cooling-lubrication methods that were tested (without a cleaning jet). [Copyright &y& Elsevier]

The objective of this article was to investigate the performance of coated carbide and low content cubic boron nitride (CBN-L) tools in finish turning of hardened steel. The tool life, cutting tool temperature, cutting forces, and surface integrity of machined workpiece achieved with both the tools under similar cutting conditions were compared. The effect of variation in cutting conditions on the performance of coated carbide and CBN inserts was also analyzed. With the selected flank wear criterion of VBmax = 200 µm, significant advantage in terms of optimum surface integrity was observed. The performance of coated carbide tools deteriorated at highest cutting speed tested, and significant chipping/breakage of the cutting edge was observed. The tool wear affected the cutting zone temperature, as well as residual stress generated on the machined surface. [ABSTRACT FROM AUTHOR]

Abstract: We reported the fabrication of the planar and channel waveguides in Na-doped calcium barium niobate (CBN) with multiple-energy oxygen-ion implantation. Multiple-energy implants can broaden the barrier width to reduce light leakage from the waveguide to the substrate through the barrier wall. The guiding modes and the near-field intensity distribution of the light were measured by the prism-coupling method and the end-facing coupling arrangement separately. The refractive index profiles of planar and channel waveguides were both typical “well+barrier” distribution, and we used the finite-difference beam propagation method (FD-BPM) to simulate the light propagation. After annealing at 200°C for 30min, the waveguide propagation loss of the planar and channel waveguides could be reduced down to ∼3.7dB/cm and ∼3.5dB/cm. The calculated results were in excellent agreement with the measured waveguide modes, indicating the feasibility of designing these devices. [Copyright &y& Elsevier]

Effect of doping of graphene either by boron (B), nitrogen (N), or co-doped by B and N is studied by density functional theory. Our extensive band structure and density of states calculations indicate that upon doping by N (electron doping), the Dirac point in the graphene band structure shifts below the Fermi level and an energy gap appears at the high symmetric K-point. On the other hand, by B (hole doping), the Dirac point shifts above the Fermi level and a gap appears. Upon co-doping of graphene by B and N, the energy gap between valence and conduction bands appears at Fermi level and the system behaves as narrow gap semiconductor. Obtained results are found to be in well agreement with available experimental findings. [ABSTRACT FROM AUTHOR]

A systematic research analysis has been applied to study the effect of dressing parameters on grinding forces, work piece roughness and wheel wear of a hybrid bond CBN grinding wheel. This paper presents some of the results achieved by the comparison between a conventional SiC dressed wheel and a grinding wheel dressed by means of a short-pulse fiber laser. The results show high technological potential for the laser dressing method compared to conventional dressing. Lower grinding forces and specific energy, with relatively the same surface roughness and lower total grinding wear (wear by dressing plus wear by grinding) are the biggest advantages of the laser dressing method over the conventional method. However, the economic aspects of laser dressing (investment on laser source and associated add-ons) at the moment, cannot justify the integration of such systems on the grinding machine for all types of applications. The next challenge is optimization of the laser dressing process to increase the efficiency of the process and expand the possible applications both from a technical and commercial point of view. [ABSTRACT FROM AUTHOR]

An investigation was carried out to explore the grinding capability of brazed type cBN grinding wheel on two engineering steel-bearing steel and high speed steel. The grinding forces were measured and the chips were collected and the surface features of ground cBN grinding wheel were examined by SEM. The SEM photographs showed that cBN grits were distributed uniformly on the peripheral wheel. The results indicate that material removal mechanisms are different for both the steel. In spite of high hardness of the bearing steel, the brazed type wheel was grind very effectively without having any wheel loading and rise of unusual forces. But while grinding the high speed steel; the tangential forces (proportional to the specific energy) were quite high due to hot hardness of the work material. The formation of chips was favourable in different mode of grinding condition. In long duration grinding test, the surface topography showed almost unchanged i.e. no grits pull out without having any substantial fracture. [ABSTRACT FROM AUTHOR]

The paper presents some results of investigation of finish machining of hardened bearing surfaces of cylindrical gear wheels. Finish machining has been performed with wedges of defined geometry made of CBN. The presented investigation results are related mainly to the wear processes of the cutting wedges. Additional results of quality examination of finish machined gear wheels have been presented, too. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the effects of cutting speed, feed rate, workpiece hardness and depth of cut on surface roughness and cutting force components in the hard turning were experimentally investigated. AISI H11 steel was hardened to (40; 45 and 50) HRC, machined using cubic boron nitride (CBN 7020 from Sandvik Company) which is essentially made of 57% CBN and 35% TiCN. Four-factor (cutting speed, feed rate, hardness and depth of cut) and three-level fractional experiment designs completed with a statistical analysis of variance (ANOVA) were performed. Mathematical models for surface roughness and cutting force components were developed using the response surface methodology (RSM). Results show that the cutting force components are influenced principally by the depth of cut and workpiece hardness; on the other hand, both feed rate and workpiece hardness have statistical significance on surface roughness. Finally, the ranges for best cutting conditions are proposed for serial industrial production. [Copyright &y& Elsevier]

Inconel 718 is known to be among the most difficult-to-machine materials due to its special properties which cause the short tool life and severe surface damages. The properties, which are responsible for poor machinability, include rapid work hardening during machining; tendency to weld with the tool material at high temperature generated during machining; the tendency to form a built-up edge during machining; and the presence of hard carbides, such as titanium carbide and niobium carbide, in their microstructure. Conventional method of machining Inconel 718 with cemented carbide tool restricts the cutting speed to a maximum 30 m/min due to the lower hot hardness of carbide tool, high temperature strength and low thermal conductivity of Inconel 718. The introduction of new coated carbide tools has increased cutting speed to 100 m/min; nevertheless, the time required to machine this alloy is still considerably high. High speed machining using advanced tool material, such as CBN, is one possible alternative for improving the productivity of this material due to its higher hot hardness in comparison with carbide tool. This paper specifically deals with surface quality generated under high speed finishing turning conditions on age-hardened Inconel 718 with focus on surface roughness, metallographic analysis of surface layer and surface damages produced by machining. Both coated and uncoated CBN tools were used in the tests, and a comparison between surfaces generated by both tools was also discussed. [ABSTRACT FROM AUTHOR]

Abstract: This letter reports about crystal structure, lattice relaxation, synthesis, and phase stability of BN–C and GaP–Si solid solution crystals. The hypothesis of atomic pair substitution is discussed and x-ray diffraction (XRD) proof is provided for the replacement of AIIIBV atomic pairs with CIV pairs. Cubic BN–diamond solid solutions underwent lattice relaxation after phase transformation leading to atomic displacement disorder. [Copyright &y& Elsevier]

In the present work, the performance of cubic boron nitride (CBN) inserts was compared with coated carbide and cryogenically treated coated/uncoated carbide inserts in terms of flank wear, surface roughness, white layer formation, and microhardness variation under dry cutting conditions for finish turning of hardened AISI H11 steel (48-49 HRC). The flank wear of CBN tools was observed to be lower than that of other inserts, but the accumulated machining time for all the four edges of carbide inserts were nearer to or better than the PCBN inserts. Results showed that tool life of carbide inserts decreased at higher cutting speeds. The surface roughness achieved under all cutting conditions for coated-carbide-treated/untreated inserts was comparable with that achieved with CBN inserts and was below 1.6 μm. The white layer formation and microhardness variation is less while turning with cryogenically treated carbide inserts than the CBN and untreated carbide. At low to medium cutting speed and feed, the performance of carbide inserts was comparable with CBN both in terms of tool life and surface integrity. [ABSTRACT FROM AUTHOR]

Abstract: This research has been conducted to study the influence of the abrasive and coolant–lubricant types on the minimum quantity lubrication (MQL) grinding performance. One type of CBN and three types of conventional wheels (corundum) have been tested. The tests have been performed in presence of fluid, air jet and eleven types of coolant–lubricants, as well as, in dry condition. The results indicate that the finest surface quality and lower grinding forces could be obtained while grinding with CBN wheel. In case of conventional wheels, the coarser and high porosity wheels induce much proper grinding results. Furthermore, grinding when utilizing MQL with oil results in higher grinding performance. [Copyright &y& Elsevier]

The present study, aims to investigate, under turning conditions of hardened AISI H11 (X38CrMoV5-1), the effects of cutting parameters on flank wear ( VB) and surface roughness ( Ra) using CBN tool. The machining experiments are conducted based on the response surface methodology (RSM). Combined effects of three cutting parameters, namely cutting speed, feed rate and cutting time on the two performance outputs (i.e. VB and Ra), are explored employing the analysis of variance (ANOVA). Optimal cutting conditions for each performance level are established and the relationship between the variables and the technological parameters is determined using a quadratic regression model. The results show that the flank wear is influenced principally by the cutting time and in the second level by the cutting speed. Also, it is that indicated that the feed rate is the dominant factor affecting workpiece surface roughness. [ABSTRACT FROM AUTHOR]

In the manufacture of precise mechanical components, which requires high me-chanical and wear resistance, the grinding process is used to give the desired finishing and to eliminate the distortion occurred during the quenching step in the steel heat treatment process. However, the grinding conditions should be appropriate so that flaws are not incorporated into the piece. New lubrication and cooling concepts for the grinding process are being researched in order to reduce costs and environmental damage caused by cutting fluids. The influences on the surface integrity and surface quality of the ABNT 4340 hardened parts have been analyzed in this research by employing the minimum quantity of lubrication (MQL), optimized and conventional cooling, different flows and velocities in the application of the cutting fluid and a super abrasive grinding wheel in the cylindrical plunge grinding process. The ABNT 4340 steel, with several industrial applications, is considered for aeronautical use due to its high strength without increasing the weight of the components. The quality analysis of the parts was done by roughness verification and electron scanning microscopy (ESM). The tangential cutting force was also verified. Regarding the different forms of the cutting fluid application, the best performance was verified for the optimized for higher speeds showing the efficiency of the nozzle used. The optimized and the MQL processes were able to maintain the surface hardness and integrity of the produced parts. The only exception occurred for the MQL condition with a cutting fluid flow rate at 40ml/h, which led to cracks and superficial burns. Grinding wheels with low CBN concentration, therefore cheaper, produced good results when associated with more efficient techniques of cutting fluid application, showing reduced wear. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a quantitative analysis of a polycrystalline cubic boron nitride tool material by electron energy-loss spectroscopy spectrum imaging acquired in dual range mode. Having both the low-loss and core-loss regions acquired nearly simultaneously provides the advantage of accurate corrections for thickness effects and thus the possibility to perform quantification calculations. This has resulted in extracted bonding maps with areal (atoms/nm2) or volumetric (atoms/nm3) densities. Spectroscopic signatures in the low-loss and core-loss energy ranges, of the elements (Al, B, C, N, Ti and O) present in the existing phases, were studied and used when extracting the element specific bonding maps by the multiple linear least squares fitting procedure. Variations of elemental concentrations across the investigated area were determined, despite of phase overlap in the beam direction or energy overlaps in the EELS spectrum. Moreover, the surface oxidation of Ti(C,N) and AlN as well as the amorphisation of α-Al2O3 is discussed. [Copyright &y& Elsevier]

Abstract: Optical ridge waveguide using calcium barium niobate (CBN) on silicon substrate for the first time is designed, fabricated and characterized for future integrated electro-optic devices. To obtain single-mode propagation, the CBN thin strip is designed to be surrounded by thick silicon dioxide layer forming a ridge waveguide. Deposition of CBN film on profiled silicon dioxide introduces spatial separation which solves the CBN etching problem. Fabrication, edge polishing and near-field mode profile measurement of the waveguide are carried out. The measurement is in good agreement with the simulation and an exact loss as low as 2.15dB/cm was obtained for the fabricated waveguide. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, various cubic boron nitride (cBN) crystal morphologies were synthesized using hexagonal boron nitride (hBN) as raw materials and Li3N, LiH, and LiNH2 as catalysts/additives under high pressure and high temperature (HPHT).These crystal shapes contain thick-plate, spherical, octahedral or hex-octahedral, flat cone and flaky hexagonal morphologies. The reasons of various crystal shapes synthesized can be summarized as follows: various catalysts/additives take on distinct properties under HPHT, which have crucial effects on the cBN crystal morphologies synthesized. Catalyst Li3N tends to grow cBN with thick-plate morphology, catalyst LiH would induce the growth of cBN tending to integrated octahedral morphology, and catalyst LiNH2 would play diverse roles for cBN crystal morphologies in various systems. [Copyright &y& Elsevier]

Abstract: We report the influence of substrate surface roughness on cubic boron nitride (cBN) film deposition under low-energy ion bombardment in an inductively coupled plasma. Silicon and cemented tungsten carbide–cobalt (WC–Co) surfaces are roughened by low-energy ion-assisted etching in a hydrogen plasma, followed by deposition in a fluorine-containing plasma. Infrared absorption coefficients are measured to be 22,000cm−1 and 17,000cm−1 for sp2-bonded BN and cBN phases, respectively, for our films. For the silicon substrates, the film growth rate and the cBN content in the film increase with increasing the surface roughness, while the amount of sp2BN phase in the film shows only a small increase. A larger surface roughness of the substrate results in a smaller contact angle of water, indicating that a higher surface free energy of the substrate contributes to enhancing growth of the cBN film. For the WC–Co substrates, the film growth rate and the cBN content in the film increase similarly by roughening the surface. [ABSTRACT FROM AUTHOR]

Nickel-based super alloys are used in a variety of applications in which high-temperature strength and resistance to creep, corrosion, and oxidation are required, such as in aircraft gas turbines, combustion chambers, and automotive engine valves. The properties that make these materials suitable for these applications also make them difficult to grind. Grinding systems for such materials are often built around vitrified cBN (cubic boron nitride) wheels to realize maximum productivity and minimum cost per part. Conditions that yield the most economical combination of stock removal rate and wheel wear are key to the successful implementation of the grinding system. Identifying the transition point for excessive wheel wear is important. The aim of this study is to compare the performance of different cBN wheels when grinding difficult-to-grind (DTG) materials by determining the 'wheel wear characteristic curve', which correlates the G-ratio to the calculated tangential force per abrasive grain. With the proposed methodology, a threshold force per grit above which the wheel wear rate increases rapidly can be quickly identified. A comparison of performance for two abrasive product formulations in the grinding of three materials is presented. The obtained results can be applied for the development of grinding applications for DTG materials. [ABSTRACT FROM AUTHOR]

Abstract: We report the feasibility of glass press molds using high-quality, thick cubic boron nitride (cBN) films prepared in a plasma jet by chemical vapor deposition. A press test using a cBN film for an optical glass is carried out at a high temperature (≥650°C), above the glass transition temperature. Surface morphology, chemical composition, and optical transparency of the glass after a press test are examined by atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersion X-ray spectroscopy, and ultraviolet-visible-near-infrared (UV-VIS-near-IR) and IR spectroscopy. The B and N concentrations at the top several nanometers of the glass increase by several at.% after a press test. This is attributed to diffusion of B and N from the film into the glass. The UV-VIS-near-IR transparency of the glass in a short wavelength range (≤900nm) decreases by several % due to light scattering at the roughened glass surface. In contrast, the IR transparency of the glass remains constant despite an increase in the surface roughness. [ABSTRACT FROM AUTHOR]

Abstract: High-quality cBN single crystals were successfully synthesized in the system of Li3N–hBN with additive LiF at high pressure and high temperature (HPHT). The lowest synthetic conditions of cBN decreased to 4.6GPa, 1320°C by employing 3wt.% LiF, and it didn''t change anymore though more than 3wt.% LiF had been added. The quality of cBN crystals improved markedly. The cBN crystals and other products were examined by X-Ray diffraction and scanning electron microscopy. The X-Ray analysis reveals that the “graphitization index” (GI) of hBN increased by adding 3wt.% LiF into the system of Li3N–hBN at HPHT. The SEM photographs show that different growth steps were formed on the cBN crystal surface in systems of Li3N–hBN and Li3N–LiF–hBN, respectively. [Copyright &y& Elsevier]