Cubic Boron Nitride Particles Research Articles

Investigation on rheological characteristics of magnetorheological shear thickening fluids mixed with micro CBN abrasive particles

The novel magnetorheological shear thickening polishing fluids (MRSTPFs) were developed by mixing micro cubic boron nitride (CBN) abrasive particles into traditional magnetorheological shear thickening fluids. MRSTPFs were constructed by uniformly fumed silica and polyethylene glycol as shear thickening fluids, carbonyl iron particles (CIPs) as ferromagnetic phase and CBN particles as abrasive phase. In this work, various MRSTPFs were prepared to explore their rheological characteristics. Sweeps of steady shear rate and dynamic shear frequency were conducted under different magnetic flux densities, respectively. A mathematical model was presented to explain shear rate variation with shear stress. The magnetorheological shear thickening mechanism was well described. The rheological experiment results have revealed that shear thickening effect was still existing in magnetic flux density. However, the increased magnetic flux density played a negative role on the shear thickening effect. Particle size optimization of CIPs was thus essential to maximize the shear thickening effect. On the other hand, with increased shear frequency, the viscoelastic feature of MRSTPFs was converted from linear to non-linear. It was found that the shear yield stress of the MRSTPFs was magnified with the stronger magnetic flux density and larger CIPs size. The investigation of rheological characteristics demonstrated that MRSTPFs could enhance polishing performance, which contributed to developing a high-efficiency and ultra-precision polishing process.

Effect of silanized stackedKevlar fiber/brass 270 wire mesh on mechanical and impact toughness of cubic boron nitride–epoxy composite

AbstractKevlar 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.

High velocity air fuel (HVAF) spraying of nickel phosphorus-coated cubic-boron nitride powders for realizing high-performance tribological coatings

High velocity air fuel (HVAF) spraying is an emergent thermal spray process, which is used in this work to realize high-performance large area tribological coatings of nickel-phosphorus cladded cubic-boron nitride (c-BN) particles. To the best of authors’ knowledge, this is the first time that HVAF has been utilized for developing Ni–P coatings reinforced with c-BN (NBN). The importance of appropriate processing was highlighted by utilizing two different nozzle configurations, for which microstructure, phase analysis and hardness results demonstrates considerable differences. Furthermore, the coatings were subjected to sliding wear tests to assess their friction and wear characteristics. Post-wear SEM analysis reveals the associated wear mechanisms. Effect of annealing on tribological performance of NBN coatings was also examined, and it is shown that optimal processing can preclude the need for post-treatment. Results ensuing from this work lay the foundation for new generation of HVAF-sprayed wear resistant metal/c-BN composite coatings for diverse applications.

Tribological and anti-corrosion performance of epoxy resin composite coatings reinforced with differently sized cubic boron nitride (CBN) particles

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.

Ultrasonic-Assisted Innovative Polyurethane Tool to Polish Mold Steel

High-quality die and mold production is becoming increasingly important in modern mass production. Surface quality is one of the most frequent and stringent customer specifications for machined parts, of which the major consideration and indication of quality is their surface roughness. In this study, a novel ball-ended polishing tool made of polyurethane impregnated with micro cubic boron nitride (CBN) was developed. The polishing tool was mounted on a three-axis machining center; the rotary polishing action was achieved via ultrasonics. Polishing experiments were conducted on specimens of hardened Stavax stainless mold steel. Four types of polishing tools – containing 10 wt% of pure CBN particles and Al2O3coated CBN with two different degrees of hardness (Shore 25 and 45) – were fabricated; the results of the experiments were compared with those obtained using a traditional elastic-ball polishing tool. It was found that the surface quality achieved using the Al2O3coated CBN tool was superior to that with pure CBN particles because the hardness of the polishing tool increased with the increase in the surface roughness of the workpiece. In addition, ultrasonic-assisted polishing yielded a better surface finish.

THICKNESS DETERMINATION AND CONTROL OF FUNCTIONAL Ni–COMPOSITE ELECTRODEPOSITED COATINGS

Surface electrochemically plated with nickel and highly inert particles provides useful applications: Ni–CeO2 as chemical catalysts, high hardness Ni–CBN (cubic boron nitride) as grinding tools, among others. The plating’s inert particles – 100 mm in size – on nickel surface need to be tightly adherent and evenly dispersed; it is therefore necessary to determine and control the coating layer’s thickness corresponding to the inert particles’ size by parameters like electrical current density and time. With 40–60 nm CeO2 particle size, Ni plating thickness is 12 mm. With 60–100 mm CBN particles, Ni plating thickness is up to 60 mm. Weight and plating thickness were determined by the weight method and Faraday's law. The difference between the two methods showed the presence of inert functional particles on composite coating. EDX method and SEM image also showed the alignment as well as the distribution of particles on the coating surface. Catalytic ability of Ni–CeO2 coating and abrasive properties of Ni–CBN coating were tested by special methods, proving composite plating method useful as catalyst sand grinding metal surface.

Fabrication and Characterization of Aluminium Boron Nitride Composite for Fins

Fins are being used to dissipate the heat from the object mainly for cooling purpose. Conventionally, In heat sinks Aluminium alloys are the common material used till date as fin material. In this preliminary research work, a new class of heat transfer material is engineered by dispersing ceramic particles in conventionally used heat transfer aluminium alloys. The fabrication of Aluminium Matrix Composites (AMC) reinforced with micro-sized cubic boron nitride (CBN) particles was prepared by bottom tapping stir casting method. In this process, 2% of magnesium was added as wetting agent for uniform dispersion of CBN. Characterizations of prepared composite specimens are carried out in optical microscope, SEM & EDX. A preliminary heat transfer study using pin fin apparatus on the fabricated Al/BN composite is investigated and their temperature distribution properties are compared. The result shows the significant enhance in heat transfer rate due to the addition of CBN particles in Aluminium alloy (AA 6061 T6).

Influence of Nano/Micro CBN Particle-Coated Tools on Rolling Contact Fatigue Performance of Hard-Machined AISI 1053 Steel

In this article, we study the influence of the cubic boron nitride (CBN) particle size in nano/micro CBN particle-coated tools on the fatigue performance of hard-machined AISI 1053 steel. The effect of the CBN particle size on the crack initiation life and the crack propagation life is reduced significantly with increased loading, whereas the crack propagation life is more influenced by the CBN particle size compared with the crack initiation life. The CBN particle size can influence the crack initiation life by 96 % and the crack propagation life by 130 %. As a result, it can influence the fatigue life by 370 % at the maximum Hertzian stress of 2,724 MPa. The results demonstrate that the CBN particle size influences the fatigue life and that the effect of the CBN particle size on the fatigue life can be lessened significantly if the loading is increased to a certain level that depends on the function of machined surfaces.

Microstructure characteristics of CBN/steel joints brazed with TiB2 modified active filler

The joint of cubic boron nitride (CBN) grits to 0·45%C steel were obtained by using TiB2 modified Ag–Cu–Ti active filler at the brazing temperature of 920°C for the holding time of 5 min. The microstructure characteristics of the brazing interface were detected by means of optical microscope, scanning electron microscope, energy dispersion spectrometer, X-ray diffraction and microhardness measuring equipment as well. It has been found that the microstructure of Ag–Cu–Ti filler layer is significantly refined by TiB2 particles. The almost well proportioned distribution of TiB2 particles in the filler layer is realised. Negative influence of TiB2 particles has not occurred on the chemical reaction of CBN particles and the filler at elevated temperatures. Reliable joining of CBN grits to 0·45%C steel is accomplished dependent on the resultant reaction products at the brazing interface.

Performance of nano/micro CBN particle coated tools in superfinish hard machining

A two-stage composite coating method has been developed for coating of nano/micro cubic boron nitride (CBN) particles on cutting tools. Since nano/micro CBN particle coated tools are more cost-effective than solid polycrystalline CBN (PCBN) tools, a comprehensive study on the coated tools is required. This paper studies the performance of these tools in superfinish hard machining. Specimens were machined by a solid PCBN tool and CBN particle coated tools with two different CBN particle size distributions: less than 0.5 and 2 μm. The specimen machined by a tool with small CBN particle coating (less than 0.5 μm) showed more compressive residual stresses and less thermal damage below the machined surface than other specimens. Furthermore, the specimen machined by a tool with small CBN particle showed less residual stress scatter than other specimens. The rolling contact fatigue life was predicted by using a rolling contact fatigue life model. The rolling contact fatigue life predictions indicate that the predicted life of the specimen machined by a tool with small CBN particle coating is longer than that of other specimens. The results thus indicate that a tool with small CBN particle coating provides better performance than other tools in superfinish hard machining.

Sintering of Vitrified Bond CBN Grinding Tool

Cubic boron nitride(CBN) is a superhard materials with many advantages and many uses. Vitrified bond CBN grinding tool is a promising abrasive tool of high performance used for high speed, high efficiency, high precision grinding with lower grinding cost and less environment pollution. Sintering of vitrified bond CBN grinding tool was investigated in this paper. The results showed that practical sintering temperature of this tool was much lower than the initial oxidation temperature of CBN particle measured by comprehensive thermal analysis. The upper limit of sintering temperature should be determined by taking account of the thermal analyzing results, heating process of CBN and its change in strength and structure. Within the sintering temperature range of the vitrified bond, relatively higher sintering temperature was beneficial to the strength of bond bridge and the holding strength between bond and CBN abrasive particles. CBN tool sintered at relatively lower temperature tended to fracture through the bond bridge, while the one sintered at higher temperature tended to fracture along the boundary between CBN abrasive grain and vitrified bond.

Experimental investigation on cubic boron nitride turning of hardened AISI 52100 steel

This study investigated the performance and wear behavior of different cubic boron nitride (CBN) tools in finish turning of hardened AISI 52100 steel. Tool performance was evaluated based on the part surface finish and the tool flank wear. Wear conditions of CBN cutting tools were primarily characterized by scanning electron microscopy (SEM). Machining results showed that low CBN content tools (CBN-L) consistently perform better than high CBN content counterparts (CBN-H), despite the CBN-L has inferior mechanical properties. The flank wear rates were proportional to cutting speed and CBN-H showed accelerated thermal wear associated with high cutting temperatures. Reducing depth of cut would only improve surface finish to CBN-L, but not to CBN-H, despite similar wear rates. The transferred layer on the flank wear land may result in adhesion of the binder compound and significantly affect the tool wear process. The metallic binder in CBN-H has stronger affinity to the transferred layer and may result in plucking-out of CBN particles and consequent severe abrasive wear.

Novel Composite CBN-TiN Coating: Synthesis and Performance Analysis

Cubic boron nitride (CBN) coating, due to its promising properties, is under development worldwide for machining and other related applications. To synthesize a continuous CBN coating by conventional vapor deposition methods (CVD/PVD), however, poses many challenges, such as metastable CBN phase stabilization, as well as the high levels of intrinsic stress developed during the growth. A novel combinatorial approach, which is under development in an effort to develop a CBN composite coating for cutting tools, is reported in this paper. The approach involves a two-step process consisting of electrostatic spray coating (ESC) of CBN particles, followed by chemical vapor infiltration (CVI) of TiN. The process is optimized to deposit a CBN-TiN composite coating with a thickness in excess of 10 μm on tungsten carbide inserts. Such coated tools have been successfully evaluated and tested for machining applications. For production on a commercial scale, the laboratory systems have been upgraded to industrial size. The outcome of scaling up from an experimental to an industrial-sized unit is reported in this paper. The industrial electrostatic spray coating unit, which can coat a batch of about 50 inserts in a couple of minutes, is currently being field tested.

Experimental investigation on CBN turning of hardened AISI 52100 steel

This study investigated the performance and wear behavior of different cubic boron nitride (CBN) tools in finish turning of hardened AISI 52100 steel. Tool performance was evaluated based on the part surface finish and the tool flank wear. Wear conditions of CBN cutting tools were primarily characterized by scanning electron microscopy (SEM). Machining results showed that low CBN content tools (CBN-L) consistently perform better than high CBN content counterparts (CBN-H), despite the CBN-L has inferior mechanical properties. The flank wear rates were proportional to cutting speed and CBN-H showed accelerated thermal wear associated with high cutting temperatures. Reducing depth of cut would only improve surface finish to CBN-L, but not to CBN-H, despite similar wear rates. The transferred layer on the flank wear land may result in adhesion of the binder compound and significantly affect the tool wear process. The metallic binder in CBN-H has stronger affinity to the transferred layer and may result in plucking out of CBN particles and consequent severe abrasive wear.