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The service performance of polycrystalline cubic boron nitride (PcBN) tools undergoes significant changes due to the deep space environment to the structure and wear behaviors of PcBN. In this paper, the effect of cryogenic treatment (CT) was studied to investigate the physical and tribological behaviors of PcBN. The hardness and wear resistance of PcBN are improved but wear forms are not affected, which are abrasive wear. The shedding of cBN played the role of micro-cutting edges, carving furrows on surfaces. As the CT duration increases, the wear rate of PcBN decreases from 2.56 × 10−8 mm3/N mm to 1.61 × 10−8 mm3/N mm for sliding against Si 3 N 4. When PcBN slid Al 2 O 3 , the lowest wear rate is 1 × 10−8 mm3/N mm which the decline reached 34 %. Due to discrepancies in physical and mechanical properties, Si 3 N 4 and YG8 balls exhibit abrasive and adhesive wear, and Al 2 O 3 shows fatigue wear. Until the fatigue failure appeared, Al 2 O 3 exhibited the lowest wear rate of 2.30 × 10−9 mm3/N mm. Among three materials, the wear rate of Si 3 N 4 was the highest. By calculating the wear rate ratio of the materials, it was concluded that the optimal removal efficiency was achieved for Si 3 N 4 and YG8 when CT duration is 24 and 48 h, respectively. [ABSTRACT FROM AUTHOR]

The monolithic PcBN composite tool materials were prepared at 5.5 GPa and 1450 ℃ with different contents of Ti3AlC2 as the binder phase. The effects of different mass fractions of Ti3AlC2 on the phase composition, microstructure, and mechanical properties of PcBN tool materials were studied. The results show that Ti3AlC2 can decompose completely to form TiC and Al-Ti alloys under high temperature and high pressure, and reacts with cBN to form AlN, TiB2, and TiC0.7N0.3 phases. TiC, AlN, TiB2, and TiC0.7N0.3 are uniformly distributed around the cBN and tightly bonded to the cBN, thereby improving the mechanical properties of PcBN. When the mass fraction of Ti3AlC2 is 25 %, the relative density, bending strength, fracture toughness, and wear ratio of PcBN reach the maximum values, which are 98.9%, 592 MPa, 6.87 MPa·m1/2and 7 350, respectively. When the mass fraction of Ti3AlC2 is 20%, the microhardness of PcBN reaches the maximum value of 4 786.7 HV.

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In this work, a combination of first-principles calculations and experiments is used to not only reveal the growth mechanism of hexagonal rod-shaped crystals TiB 2 and its theoretical influencing factors, but also to experimentally regulate the growth of TiB 2 rod-shaped crystals to obtain polycrystalline cubic boron nitride (PcBN) composites with excellent comprehensive mechanical properties. The calculation results reveal that under Ti-rich or B-rich conditions, both the surface energies of (0001) and (10 1 ̄ 0) are lower than the surface energy of (11 2 ̄ 0). The growth of TiB 2 is interpreted at the atomic level as being composed of (0001) and (10 1 ̄ 0) surfaces, and it preferentially grows as rod crystals along the (0001) crystal plane. The calculations further indicate that the hexagonal morphology of TiB 2 is determined by the atomic concentration within the melt. It exhibits a higher propensity for nucleation under Ti-rich conditions than under B-rich conditions. And it is predicted that a lower relative concentration of Ti atoms promotes the growth of TiB 2 into hexagonal rod crystals. In addition, PcBN composites with TiB 2 reinforced phase are synthesized in situ by modulating the Ti-Al molar ratio. The experimental results demonstrate that as the concentration of Ti atoms decreases, the nucleation of TiB 2 decreases, while the growth of TiB 2 rod crystals increases, which aligns with the predicted calculations. Moreover, the presence of rod crystals greatly enhances the densities and flexural strength of PcBN composites. When the Ti-Al molar ratio is adjusted to 1:2, a substantial quantity of high-quality TiB 2 rod crystals are cultivated, leading to PcBN composites exhibiting outstanding mechanical properties. [ABSTRACT FROM AUTHOR]

The problems of tool wear and machining economy are prominent in hard cutting process. Clean cutting technology can effectively improve the cutting environment. The cutting performance of coated tools and PCBN tools is investigated in clean hard cutting of H13 steel (55 ± 1 HRC) under dry, cold air, and cryogenic liquid nitrogen conditions. The machining economics are also analyzed to investigate the feasibility of improving tool life through clean cutting technology. From the perspective of machining economy, the machining cost of cold air cutting is lower than that of dry cutting and liquid nitrogen cutting. The coated tool is suitable for cutting under cryogenic liquid nitrogen condition. Compared with dry cutting, the coated tool life is increased by 55.6% at cryogenic liquid nitrogen condition. PCBN tools are prone to chipping at cryogenic temperature, resulting in early failure. PCBN tools achieve the longest tool life in cold air cutting. [ABSTRACT FROM AUTHOR]

Tribological properties are the significant factors to evaluate the application of polycrystalline cubic boron nitride(PcBN) with hard materials in vacuum conditions. In the current paper, the tribological properties of PcBN and WC-Co cemented carbide (YG8) during the sliding process are carried out under different loads in vacuum by ball-disk friction and wear experiments. The wear tracks of PcBN and wear scars of YG8 were characterized. The results show that the wear mechanisms of PcBN in vacuum are mainly abrasive wear and adhesive wear. Furthermore, furrows are also detected on the surface of YG8 balls due to the plowing of exfoliated cubic boron nitride. As a result, abrasive wear is the failure form of YG8 ball. The average CoF is negatively correlated with the loads. Moreover, the relationship between friction and wear is discussed deeply. The wear rate of YG8 ball is positively correlated with the load. Additionally, the wear rate ratio of PcBN and YG8 indicates that higher loads can promote the wear rate of YG8, but it also leads to the rapid wear of PcBN. The results could provide significant instructions for the regulation and control of the tribological properties of PcBN in the coming outer space exploration activities. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride (PcBN) is the designation given to composites constituted by cBN hard particles within a ceramic/metallic matrix. These composites are normally processed in severe pressure and temperature conditions to achieve full densification and prevent hexagonal BN formation, which would decrease the composite hardness. In this work, the Spark Plasma Sintering (SPS) technique was investigated as an alternative to sinter cBN-TiCN based composites, with and without addition of metallic Ni. The initial compositions were selected according with calculated phase diagrams, using the Thermo-calc software. The thermal behavior during SPS was studied up to 2000°C, namely the densification, reactivity and phase transformations. A larger densification was achieved with Ni addition, but full removal of open porosity was only possible at 1700 °C, where the cBN phase transformation to hBN completely occurred. In agreement with the thermodynamic calculations, other matrix phases, as TiB 2 and Ni 3 B, were formed during sintering. • Phase diagrams for BN-TiCN-Ni systems were calculated using Thermo-Calc Software. • Addition of 10 wt% Ni to BN-TiCN increased the shrinkage rate during SPS. • The metallic Ni completely reacted with BN during SPS to form Ni 3 B. • The matrix region of composites is constituted by Ni 3 B, TiCN and residual TiB 2 phases. • The thermodynamic software is a very useful tool for microstructural design of BN composites. [ABSTRACT FROM AUTHOR]

Friction stir welding is a solid-state joining process used to weld various materials. Tool life is an important consideration when welding strong metals with the Friction stir welding technique (FSW). The current research aims to calculate tool life by mathematical derivation and simulation using ANSYS transient structural analysis. There are two tool materials and five-pin profiles to consider. The calculated tool life using mathematical formulation is within 15% of the simulation outcome. Further changes are made to the simulation to make the tool life estimate more realistic under FSW’s operation. PcBN tool has superior mechanical properties over the tungsten carbide tool, so the procedure started with the tungsten carbide tool. The conical pin profile is giving 31466 cycles of tool life, which is 70 min run time while working at 450 rpm rotational speed. As a result, for high-strength materials joining, the tool must be chosen based on tool life parameters. The addition of a 1.5 mm fillet at the pin-to-shoulder junction has improved the tool life by 1147 cycles. The PcBN tool is simulated with a conical tool with new pin profiles of conical with grooves and cylindrical fillet with grooves. The maximum tool life of 94018 cycles is obtained for the conical PcBN tool.

The 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) is regarded as a superior bioceramic being extensively used in modern denture restoration. However, the material possesses extremely poor machinability and are prone to serious cracking and failure formation due to its exceptionally high hardness and inherent brittleness. Hard milling is a feasible strategy to shape fully-sintered 3Y-TZP to desired quality and target dimensions. The present paper aims to study the milling behaviors and mechanisms of 3Y-TZP ceramics by using superhard PCD and PCBN tools. The fundamental milling responses, including cutting forces, temperatures, and surface morphologies, were all examined. The parametric effects on the 3Y-TZP machinability outputs were addressed. A particular focus is placed on comparing the cutting performances of different tools in milling 3Y-TZP. It is found that the PCD tool outperforms the PCBN tool from the perspective of reducing cutting forces, specific cutting energy consumption, and milling temperatures. To get smooth surface morphologies with minimal damage, the spindle speed lower than 5000 rpm and the feed per tooth lower than 9 μm/z should be adopted for the PCD tools. However, under large milling parameters, the PCBN tools show advantages in ensuring the stability of machined surface quality for 3Y-TZP ceramics over the PCD ones. [ABSTRACT FROM AUTHOR]

This paper contributes to broadening the knowledge regarding coated PCBN tool wear in the finish turning operations of nickel-based superalloy GH4202. Three different coating PCBN tools (uncoated, TiN, and TiAlN) were used for finishing turning of superalloy GH4202. Cutting tests were carried out at a wide range of cutting speeds (vc = 50–400 m/min). Two different cutting conditions (dry and wet cutting) were also introduced. Aspects of tool wear and generated surface quality were studied. It was found that the protective function of the coating was limited only to the low cutting speed range. EDS analysis was used to analyze the wear mechanism under different cutting speeds. Different coatings exhibited different performance under different working conditions. The TiN coating was the most sensitive to the cutting coolant, and the uncoated tool was the most stable. Significant deposition of wear products was observed at high cutting speeds with the addition of cutting coolant. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride (PCBN) materials were prepared to use cBN, TiC, Ti, and Al as raw materials under high temperatures and high pressures with varying sintering temperatures (1300–1600 °C) and holding times (6–15 min). The study analysed the reaction synthesis mechanism and interface bonding state of the PCBN materials and investigated the effects of sintering temperature and holding time on the mechanical properties and cutting performance of the PCBN materials. The results show that under high-temperature and high-pressure conditions, metal atoms' diffusion was accelerated, allowing the binder and cBN to react quickly, forming a new binding phase The new bonding phase had a strong bond between the cBN grains of PCBN, resulting in a dense composite material with excellent mechanical properties. The PCBN material's mechanical properties initially increased and then weakened with an increase in sintering temperature. At 1500 °C, the material's flexural strength and hardness reached 970.9 MPa and 3489.2 Hv, respectively. The mechanical properties of the PCBN material increased with an increase in holding time, with a holding time of 15 min resulting in flexural strength and hardness of 980.2 MPa and 3529.1 Hv, respectively. The PCBN tool material prepared at 1500 °C and 12-min holding time exhibited the best cutting performance. During a 10 km cutting length of cast iron, the tool wear was only 0.26 mm. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride (PcBN) composites were synthesized in situ with TiB2, TiN, and Sialon as binders under ultrahigh temperature (1550°C) and high pressure (5.5 GPa). X‐ray diffractometry, universal testing machine, field emission scanning electron microscopy, and transmission electron microscopy were used to study the effect of Sialon content (0%, 20%, 40%, 60%, and 80% by mass of binder) on the phase composition, microstructure, and mechanical properties of PcBN composites. The results show that the main phases in the system are lamellar TiN, needle‐rodlike TiB2, and irregular long‐rodlike Sialon. Some TiB2 grows along the (1 0 −1 0) face, and Sialon grows along the (0 0 0 1) face. The density and mechanical properties of the sintered product are significantly improved due to the formation of Sialon. When the content of Sialon is 60%, the binder is uniformly distributed, the cBN interface is well bonded, and the density is the highest. At this time, the strength reaches the maximum 34.57 GPa, the fracture toughness is 6.82 MPa m1/2, and the flexural strength reaches the maximum 870.79 MPa. On the whole, cBN composites have excellent prospects for future applications in cutting inserts due to their excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitrides (PcBNs) are composites widely used as cutting tool materials due to their exceptional high hardness and wear resistance. Investigation of their micromechanical properties is key for optimizing PcBN's performance through microstructural design. Within this context, high-speed nanoindentation is proposed and implemented, for three different PcBN grades, to correlate microstructure with local mechanical properties. A total of 40,000 imprints were performed in each grade. The obtained mechanical maps and data sets are statistically treated following two deconvolution approaches: 1D and 2D Gaussian fitting. The use of high-speed nanoindentation is validated not only by the reliable assessment of the intrinsic mechanical properties of cBN particles, binder and interphase region, but also by the successful mirroring of microstructural assemblage within the mechanical maps attained. Comparison of the results determined from 1D and 2D gaussian representations are in satisfactory agreement. Nevertheless, some difficulties and disparity between them arises when involving fine-grained microstructures. [Display omitted] • Mechanical property maps replicate the microstructure assemblage of PcBN grades. • 1D and 2D representations also depict multiphase material microstructure. • Nanoindentation is validated for assessing H and E of PcBN constitutive phases. • Good agreement is generally found between 1D and 2D statistical analysis results. • Demonstration of the presence of a third composite-like/interface-related phase. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride (PcBN) with excellent mechanical properties was sintered by using high activity TiC0.5 and metal aluminum as binder at high temperature and pressure. The effects of sintering temperature on phase composition, microstructure, relative density and mechanical properties of PcBN composites were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy spectrum analysis. The results show that, under the conditions of low reaction temperature of 1400°C and holding time of 10 min, excellent composite properties of PcBN sintered material were obtained. The reinforced phases such as Ti(C, N), TiB2 and AlN were stably presented in the sintered body. To be specific, the microhardness, flexural strength and fracture toughness of the sintered body first increased and then decreased with the increasing sintering temperature, as well as posessing a high fracture toughness, which were 39.74 GPa, 1217 MPa and 8.78 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

Conventional cemented carbide is recommended for machining Ti6Al4V. However, polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (pcBN) also show promise. Demands for higher productivity accelerate diffusional dissolution and chemically driven wear mechanisms in these tool materials. This study investigates active wear mechanisms by studying the interactions between Ti6Al4V and PCD, pcBN, and cemented carbide tools in diffusion couples at temperatures from 900° to 1300°C. All tool materials suffered from diffusion to varying degrees, and different chemical reactions occurred. Titanium carbide with minor vanadium alloying (Ti,V)C reaction products act as diffusion barriers when using PCD and cemented carbide, while the reaction products acting as diffusion barrier in pcBN is (Ti,V)B 2. The presence of Mo and W in binder sites of pcBN reduces diffusional dissolution of cBN. Diffusion simulations agreed well with microscopy investigations and were enabled by the known temperature and pressure conditions of the static diffusion couples. [ABSTRACT FROM AUTHOR]

Machining processes of Ni-based alloys typically lead to very high wear rates and significant heat generation, even when small material removal rates are considered. Despite the increasing usage of PCBN tools in the machining of Ni-based superalloys, further research is required in order to better understand the associated benefits. In this work, the machinability of Inconel 718 in two different delivered strength conditions has been evaluated using PCBN tools through instrumented turning operations. Tool-life has been explored and linked to cutting force evolution. Numerical simulation of the turning operations has revealed important towards tool wear modelling. [ABSTRACT FROM AUTHOR]

The cBN, Zr, and Al powders were mixed to synthesize PcBN (polycrystalline cubic boron nitride) tool material under high-temperature, ultra-high-pressure conditions. X-ray diffraction and scanning electron microscopy were used to analyze the phase composition and microstructure of the tool material. The mechanical properties and microstructural trends of the tool material at various temperatures were investigated. Research indicates the formation of new phases in the PcBN material following high-temperature and ultra-high-pressure sintering. However, there is no significant difference in the types of formed new phases, all of which consist of BN, ZrB 2 , ZrN, and AlN. The sintering density of the tool material was higher at 1500 °C and 1600 °C, and the mechanical properties improved with increasing sintering temperature. The highest number of tool processing parts made of PcBN tool material synthesized at 1600 °C is 232. • PcBN materials sintered between 1500 °C and 1600 °C exhibit optimal and similar mechanical properties, with the fracture toughness, strength, and impact resistance of the PcBN tool material sintered at 1600 °C reaching their highest values at 7.2 MPa1/2, 923.2 MPa, and 75 times, respectively. • The microhardness of PcBN materials increases with the rise in sintering temperature, from 30.35 GPa at 1300 °C to 33.84 GPa at 1600 °C. [ABSTRACT FROM AUTHOR]

Using WC–B4C–Al2O3 as a binder, polycrystalline cubic boron nitride (PCBN) composite materials were synthesized under high temperature and ultra-high pressure conditions. X-ray diffraction (XRD) and scanning electron microscope (SEM) was used to analyze the phase composition and microstructure of the composite material. At the same time, the porosity, microhardness, flexural strength, and abrasion ratio of the composite material were tested. The research results show that at ultra-high pressure (6 GPa) and temperature between 1250 and 1550°C, the phase components in PCBN are mainly composed of BN, WB2, WB, and Al2O3. During low-temperature sintering, the internal structure of the sample is loose, with holes and gaps, resulting in poor compactness, low bending strength, and low microhardness. With the increase of temperature, the compactness, flexural strength, and microhardness of PCBN are obviously enhanced. When the sintering temperature is 1550°C, the comprehensive mechanical properties of PCBN are the best, with microhardness of 38.6 GPa, flexural strength of 789.6 MPa, and wear ratio of 9371. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (cBN) is an important material in the cutting and metal processing industries due to its exceptional hardness and high thermal stability, which allows it to withstand temperatures up to 1400 °C without decomposing. These properties make cBN and, with that, polycrystalline cBN (PcBN) ideal materials for high-speed machining and other applications, resulting in increased efficiency and reduced costs in production processes. Despite its established importance, the possibility of phase transformations into hexagonal boron nitride phases or partial amorphization during industrial PcBN grinding processes remains unclear and, due to the deteriorated mechanical characteristics, raised recently some concerns about possible losses of cBN's hardness, wear resistance, and abrasive properties. In order to address this issue and for identifying such potential structural changes, a commercial PcBN grade was exposed to near-industrial grinding process conditions and then characterized in detail by conventional (scanning) transmission electron microscopy (S)TEM and (scanning) electron diffraction techniques. To understand the influence of the PcBN machining on the material, the grinding process also needs to be assessed via the identification of chip formation mechanisms, which is as well addressed in this work. The main outcome of this study, combining a material analysis and a manufacturing technology point of view, is that there is so far no evidence of any structural instabilities of PcBN under usual processing conditions. • Investigations of the material removal in PcBN from a manufacturing and a materialographic point of view were combined. • An assessment of the structural stability was carried out via (S)TEM investigations, among others. • No structural instabilities under usual processing conditions were identified. [ABSTRACT FROM AUTHOR]

We present a two-step method to achieve high-strength PCBN-M42 joints by employing a pre-melted CuNi layer combined with a Ti interlayer. Reliable interface bonding with PCBN is established through the Cu-Ni-Ti eutectic reaction while effectively retaining a considerable solid solution content within the joint, thus significantly enhancing the joint strength. [Display omitted] • A PCBN-M42 solid solution-based brazed joint was achieved via two-step method. • The CuNi barrier layer hindered further diffusion and reaction of Ti. • The Cu-Ni-Ti eutectic reaction enabled interface bonding with PCBN. • The (Cu, Ni, Fe) solid solution within the joint enhanced the shear strength. [ABSTRACT FROM AUTHOR]

In order to understand the surface and interface conditions of polycrystalline cubic boron nitride (PcBN) sliding against bearing steel in vacuum environments, the effects of different loads on the tribological behaviors of PcBN and bearing steel AISI 52100 were studied deeply in a vacuum tribometer. Furthermore, the wear tracks of PcBN and the wear scars of AISI 52100 were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the stable coefficient of friction (CoF) of the tribopair experiences a decrease first and then an increase with the increase in loads from 2 N to 15 N. The adhesive layer increases with the increase in loads, and the formation of adhesive layer contributes to the change of CoF and wear rate of counterpart balls. The adhesive layer is formed due to the combination of high contact stress and high temperature. Meanwhile, the exfoliated cubic boron nitride grains are embedded into the adhesive layer as abrasive grains, resulting in abrasive wear. Thus, the main wear mechanisms are adhesive wear and abrasive wear. [ABSTRACT FROM AUTHOR]

Tools made of polycrystalline cubic boron nitride (PcBN) are usually prepared with a rake face chamfer to increase the performance in hard turning. This chamfer is produced by a tool grinding process. The preparation of the cutting edge itself considering the process and material properties offers further potential for increasing tool performance. In this paper, the rounding of the cutting edge is produced by the already established and highly productive tool grinding process instead of using conventionally processes such as brushing or drag finishing. Therefore, the rounding is approximated by multiple ground chamfers. The influence of the cutting edge microgeometry on the thermomechanical load is investigated by finite element method. By enlarging the microgeometry, the mechanical stress on the tool is significantly reduced. However, an increase in the size of the cutting edge rounding is also linked to an increase in the thermal tool load. [ABSTRACT FROM AUTHOR]

Friction stir welding is a solid-state joining/processing technique that offers high strength and productivity, resulting in a microstructure similar to hot working cycles. However, high melting temperature metals such as steels cause excessive wear over welding tools, representing a significant economic issue. Most studies conducted in steels have used polycrystalline cubic boron nitride (PCBN) and W-Re composite tools, which offer a combination of high strength and hardness at high temperatures, along with high-temperature stability. However, even those tools are susceptible to tool wear. In the present study, experimental data was collected during friction stir processing of X70 grade pipeline steel plates, using W-Re and PCBN composite tools under well-controlled conditions. Profilometry and optical microscopy were used to quantify the volume loss at the welding tool due to the number of plunges and the welded distance. Torque and transverse force at the welding tool and the welded bead width were measured and related to the wear process. Tool contamination in boron-nitrogen particles and dissolved tungsten was identified at the stir and hard zones, more substantial at the latter. [ABSTRACT FROM AUTHOR]

In this paper, polycrystalline cubic boron nitride (PCBN) was prepared under a high temperature and an ultra-high pressure. The influence of different sintering temperature on composition, microstructure, porosity and mechanical properties of the PCBN were investigated by means of X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and universal mechanical testing machine. The results showed that the main phase were identified as cBN, α-Si3N4, β-Si3N4, TiN and TiB2. The cBN grains connect with each other by the reaction product. As the sintering temperature increases, the hardness of the sample increased, and its bending strength increase first and then decrease. When the sintering temperature was 1600°C, PCBN presented the best comprehensive performance, the hardness and bending strength were 32.2 GPa and 1022.5 MPa, respectively. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) of nickel-based alloys can provide joints with improved corrosion resistance and mechanical properties that are deteriorated significantly during fusion welding of these alloys. However, rapid wear and poor longevity of tools are major concerns for FSW of nickel-based alloys. Polycrystalline cubic Boron Nitride (pcBN) has emerged as an alternative tool material due to its enhanced strength and stiffness but its use for FSW of nickel-based alloys is rarely explored. An investigation is therefore undertaken to examine FSW of Inconel 625, which is a commonly used nickel-based alloy, by experimental investigation and computational process modelling. The potential failure mechanisms of pcBN tools during FSW of Inconel 625 are examined. The results showed that the thermal softening of the tungsten-rhenium binder phase and dissolution of tungsten into Inconel 625 are potential mechanisms to early wear and failure of the pcBN tools for FSW of Inconel 625. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride(PcBN) was prepared under a high temperature and an ultra-high pressure using an in situ synthesis method. The influence of sintering temperature on composition, micro-structure, relative density, porosity and mechanical property of the PcBN was investigated by means of X-ray diffraction(XRD), field scanning electron microscopy(FSEM) and energy dispersive spectroscopy(EDS). The results show that the composition of PcBN is translated from intermediate phases to stable phases consist of TiB2, h(hexagonal) AlN and TiN when increasing the sintering temperature in the range of 1400-1600℃ under ultrahigh pressure of 5.5GPa. The cBN particles connect with each other by the reaction product. With the increase of the sintering temperature, the length of rod-shaped crystals of strengthening phase TiB2 decreases and the pore in surface reduces. There exist the extraction and fracture mechanism of the rod-shaped crystals in the fracture process. The porosity is prominent reducing and the relative density increases when increasing the sintering temperature. With further increasing the sintering temperature to 1600℃, the PcBN exhibits optimal comprehensive mechanical properties with a micro-hardness of 44.1GPa and a flexural strength of 859.3MPa.

In this paper, polycrystalline cubic boron nitride (PcBN) with Ti 3 AlC 2 –Al as the compound binder was manufactured by high-temperature and high-pressure (HTHP) method. Effects of Ti 3 AlC 2 decomposition on PcBN microstructural features and mechanical properties at different sintering temperatures were systematically analyzed. Results revealed that sintering temperature of 1350 °C was critical temperature for complete Ti 3 AlC 2 decomposition under HTHP conditions. Sintering driving force improved with increasing temperature, resulting in significant enhancement of PcBN compactness. In addition, decomposition products of Ti 3 AlC 2 reacted with cBN to form TiC, TiB 2 , and AlN, improving the adhesion between cBN grains. At 1450 °C, as-prepared composites with the highest relative density value (99.6%), bending strength (586.22 MPa) and Vickers hardness (48.8 GPa) were attained. Moreover, at 1300 °C, fracture toughness of PcBN was 7.18 MPa m1/2. [ABSTRACT FROM AUTHOR]

Cutting vibration is affected by many factors and is nonlinear, so it is difficult to accurately establish a cutting vibration model by mathematical methods. This study uses BP neural network to predict the vibration of hardened steel turning. The vibration data of cutting under five parameters, such as cutting speed, feed rate, cutting depth, corner radius, and workpiece hardness, were collected. A BP neural network model was constructed by considering the prediction accuracy and running time, the model was trained based on the experiments data, and the prediction accuracy of the model was verified. It was found that the relative error of the predicted results is less than 10%, which is basically consistent with the vibration displacement under working conditions. The prediction of vibration amplitude provides a basis for parameter selection to improve the accuracy of hardened steel turning. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride (PcBN) is the second hardest material after diamond. Because of its unique properties, PcBN is extensively used as a cutting tool material for the machining of hardened steels. Pulsed laser ablation (PLA) offers the possibility to generate tailored microgeometries on PcBN tools and can thereby increase tool performance. However, the thermal response of PcBN materials to the laser ablation and the laser effeciency in laser machining is not known in dependency of certain PcBN grade characteristics. In this paper the influence of different laser sources in the short and ultrashort pulse duration regime is investigated for a wide number of PcBN grades. Thermally induced surface alterations are examined in detail and connected with the functional performance of the material. It could be shown that a careful parameter definition is crucial for enhancing the performance of laser prepared PcBN cutting tools. [ABSTRACT FROM AUTHOR]

Ti-5553, with its high strength and toughness, has been widely used in the aerospace industry as a novel aerospace alloy. High hardness, strong chemical affinity, and low thermal conductivity are the main reasons for its classification as a difficult-to-cut material. Although significant work has been performed to analyze the machinability of Ti-5553, the oxidation behavior of Ti-5553 and tool materials during the cutting process has received little attention. For this study, cemented carbide (H13A) and PCBN (BZN9000) were selected as cutting tool materials with Ti-5553 as a workpiece material. Oxidation simulation experiments were carried out in a high-temperature resistance furnace. Changes in oxidation mass gain and hardness were measured and recorded. X-ray diffraction and scanning electron microscopy were employed to detect the oxidation products and micro-morphology of the oxide layer, respectively. Based on these measurements, the oxidation behavior of the materials was analyzed and the causes of oxidative wear of the tool and workpiece materials during the cutting process were identified to provide theoretical support for Ti-5553 cutting and tool development. [ABSTRACT FROM AUTHOR]

Polycrystalline cubic boron nitride (PcBN) reinforced by different morphologic titanium diboride (TiB2) was in situ synthesized in the temperature range of 1100-1600 °C under an ultra-high pressure of 5.5 GPa in cBN-Ti-Al system. The composition and microstructure of PcBN composites were investigated by x-ray diffractometry, scanning electron microscopy and energy-dispersive spectroscopy. The mechanism and influencing factors of TiB2 microstructure formation with different morphologies were analyzed. The mechanical properties of PcBN were also tested and analyzed. The results showed that the microstructure of TiB2 evolves from whisker to plate and rod to granular as the temperature increases. Under the combined effects of phase composition, relative density and TiB2 morphology, the microhardness of PcBN increased continuously, while the flexural strength first increased and then decreased. The high flexural strength was obtained at 1300 and 1400 °C, which were 840.39 and 823.32 MPa, respectively. [ABSTRACT FROM AUTHOR]

This study investigates machining superalloy Inconel 718 with polycrystalline cubic boron nitride (pcBN) tooling both numerically and experimentally. Particular attention is given to mechanical and thermal stresses in the cutting tool arising from segmented chip formation and associated forces and temperatures. The temperature dependence of the mechanical properties of pcBN has been investigated and incorporated into a numerical model. In order to capture the dynamic loads due to a serrated chip formation, the Johnson–Cook damage model has been used. The extreme deformations during a machining process often results in a numerical difficulties due to a distorted elements. This paper uses the coupled Eulerian–Lagrangian (CEL) formulation in Abaqus/Explicit, where the workpiece is modelled with the Eulerian formulation and the cutting tool by the Lagrangian one. This CEL formulation enables to completely avoid mesh distortion. The finite element simulation results are validated via comparison of the modelled static and dynamic cutting forces and thermal loads induced into the cutting tool. The numerical model predicts a temperature of 1100–1200 ∘C at the cutting interface, which is in line with experimental determined data. The principal stresses at the rake up to 300 MPa are recorded, whereas higher level of stresses up to 450 MPa are found in the notch region of the tool, well correlated with experimental observation. [ABSTRACT FROM AUTHOR]

In this paper, Polycrystalline cubic boron nitride (PcBN) is prepared under a high temperature and an ultra‐high pressure. The influence of different titanium (Ti) content on composition, microstructure, porosity and mechanical property of the PcBN is investigated by means of x‐ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The results show that, with the addition of titanium, the cubic boron nitride (cBN) particles are connected with each other by the product phases β‐Si3N4, TiN and TiB2 under the pressure of 5.5 GPa and the temperature of 1600 °C. As the increase of titanium content in the system, the amount of rod‐like crystal β‐Si3N4 and TiB2 formed in the system increases, while the porosity remarkably decreases. When the titanium content is 13 wt%, PcBN presents the best comprehensive performance, hardness and flexural strength are 29.2 GPa and 1022.5 MPa, respectively. [ABSTRACT FROM AUTHOR]

The present study compares the performance of three different cutting tools, viz., PCBN, mixed ceramic and coated carbide tool in finish turning of hardened D2 tool steel in terms of tool wear, surface roughness, and economic feasibility under dry cutting conditions. Results showed that tool life of PCBN inserts was better than mixed ceramic and coated carbide inserts. The flank wear of PCBN tools was observed to be lower than mixed ceramic and coated carbide inserts. The surface roughness achieved under all cutting conditions for mixed ceramic and coated-carbide inserts was comparable with that achieved with PCBN inserts and was below 1.6μm. Experimental results showed that the wear mechanism of ceramic tool is pre-dominantly abrasive wear at lower speeds and abrasive wear followed by adhesive wear at medium and higher speeds and for PCBN tools the dominant wear mechanism is abrasive wear and cratering at lower speeds followed by adhesive wear at higher speeds. For carbide tool the dominant wear mechanism was abrasive wear and cratering at lower speeds followed by adhesion and chipping at higher speeds. Obtained results revealed that PCBN tools can outperform both ceramic and carbide tools in terms of tool life under different machinability criteria used.

Sustainability is a concept which is widely considered nowadays, including in factories where machining operations are present. The search for methods able to improve the performance of industrial processes without damaging the environment or the worker's health has been the main goal of several investigations. In this context, cryogenic machining is a technique that has been studied as an alternative to the use of mineral oil-based cutting fluids, mainly in the machining of titanium and nickel alloys. Investigations on the cryogenic machining of hard tool steels are still scarce in the literature. This article presents results from a series of turning trials under dry and cryogenic conditions using a hardened AISI D6 tool steel bar (57 HRC) as the workpiece. For the cryogenic machining tests, liquid nitrogen was delivered to the flank face, rake face and on both faces of PCBN inserts. The main cutting parameters (cutting speed, feed rate, and depth of cut) were kept constant during the trials. Tool wear and chip morphology were the output variables studied. The results show that the liquid nitrogen was able to reduce the cutting tool wear, providing a tool lifetime around 50% longer compared with the dry process. Moreover, the frequency of chip segmentation was diminished under cryogenic conditions in comparison with the dry process. [ABSTRACT FROM AUTHOR]

Sustainability is a concept which is widely considered nowadays, including in factories where machining operations are present. The search for methods able to improve the performance of industrial processes without damaging the environment or the worker's health has been the main goal of several investigations. In this context, cryogenic machining is a technique that has been studied as an alternative to the use of mineral oil-based cutting fluids, mainly in the machining of titanium and nickel alloys. Investigations on the cryogenic machining of hard tool steels are still scarce in the literature. This article presents results from a series of turning trials under dry and cryogenic conditions using a hardened AISI D6 tool steel bar (57 HRC) as the workpiece. For the cryogenic machining tests, liquid nitrogen was delivered to the flank face, rake face and on both faces of PCBN inserts. The main cutting parameters (cutting speed, feed rate, and depth of cut) were kept constant during the trials. Tool wear and chip morphology were the output variables studied. The results show that the liquid nitrogen was able to reduce the cutting tool wear, providing a tool lifetime around 50% longer compared with the dry process. Moreover, the frequency of chip segmentation was diminished under cryogenic conditions in comparison with the dry process. [ABSTRACT FROM AUTHOR]