磨料表面镀覆对陶瓷结合剂超硬磨具强度的影响

在陶瓷结合剂超硬磨具的烧结过程中，超硬磨料易受到陶瓷结合剂中某些成分的腐蚀或受到热损伤，在超硬磨料表面涂覆一层保护层，既可减轻或避免腐蚀和热损伤，还可改善磨料与结合剂之间的结合状况。文章主要对各种镀层的金刚石、CBN磨料与陶瓷结合剂按一定的比例热压烧结进行了分析说明，并测定了其抗折强度，研究了各镀层对磨具抗折强度的影响。     

纳米陶瓷结合剂超硬磨具的制造工艺

纳米陶瓷结合剂是一种新型的超硬磨具结合剂,采用它能显著降低磨具烧结温度,大幅度提高制品的强度、韧性和耐磨性,且气孔可控,为陶瓷结合剂的应用开拓了一个崭新的领域.文章阐述了纳米陶瓷的性能及应用.结果表明:纳米陶瓷结合剂抗折强度高于100MPa,经过烧结,纳米陶瓷结合剂与金刚石和cBN超硬磨料润湿性良好、结合力大,在烧结过程中与超硬磨料不发生反应、不腐蚀损伤超硬磨料.成功用于磨削PCD复合片的金刚石陶瓷砂轮.     

陶瓷结合剂CBN磨具强度的影响因素研究

通过陶瓷结合剂本身强度、热膨胀系数与CBN(立方氮化硼)磨料的匹配性以及陶瓷结合剂CBN磨具的烧成温度等几方面对影响陶瓷结合剂CBN磨具强度的主要因素进行了探讨.研究结果表明:陶瓷结合剂的强度是影响CBN磨具强度的一个因素,但陶瓷结合剂本身强度的高低不是CBN磨具强度的唯一保证;结合剂与CBN磨料热膨胀系数的匹配性是影响CBN磨具强度的一个重要因素.通过实验发现,结合剂与CBN磨料的热膨胀系数之差应不大于5.2×10-6/℃;在一定烧结温度范围内,适当提高烧结温度,有利于提高结合剂桥相本身强度及结合剂与CBN磨料的结合强度.     

陶瓷结合剂cBN磨具的研究现状及发展趋势

陶瓷结合剂立方氮化硼(cBN)磨具的近年来研究越来越受到重视。简要介绍了国内外在陶瓷结合剂cBN磨具方面的最新成果。提出陶瓷结合剂目前研究的主要结构体系。讨论了陶瓷结合剂cBN磨具性能研究的方法和研究中存在的问题。最后指出陶瓷结合剂cBN磨具的发展方向。     

PbO对陶瓷结合剂性能的影响研究

与其他结合剂相比,陶瓷结合剂具有散热好、易于排屑、成本低等优点,陶瓷结合剂在超硬材料磨具行业应用广泛。本文研究PbO对陶瓷结合剂性能的影响,通过向基础陶瓷结合剂中加入不同百分含量的PbO,对其耐火度进行了测定,利用微机差热膨胀仪、洛氏硬度计、微机控制电子万能试验机对加入不同量PbO结合剂的热膨胀系数和加入磨料后磨具的洛氏硬度和抗折强度进行了研究测试,再用体视显微镜对测过抗折强度的磨具试样进行断面观测分析。实验所得结果显示:适当加入少量添加剂PbO能显著降低结合剂的耐火度,加入超过10%或更多对其耐火度影响不大。与不加和加其它量相比,当添加剂添加量为5%时,加磨料后烧成的磨具具有较高的抗折强度和洛氏硬度;结合剂中加入添加剂PbO后,其热膨胀系数有所增大。通过体视显微镜断面观测可观察到,当加入PbO量过多时会有发泡产生。综合以上因素,PbO为陶瓷结合剂添加剂时,其添加量应控制在5%左右。     

金属结合剂烧结磨具孔隙度与磨具性能之间关系的探讨

金属结合剂超硬材料磨具以其长的使用寿命和更适合于加工硬脆非金属材料而著称,但其较低的自锐性和不易修整的特点使其在应用上受到了一定的限制。在分析了烧结型超硬磨具磨削中出现问题的原因之后,通过实验对磨具性能与热压温度的关系、不同孔隙度对磨具力学性能的影响以及磨料种类的不同在磨具中的作用进行了实验研究。结果表明,孔隙度增加会降低磨具的硬度与强度,表面镀覆超硬cBN可以大大改善高孔隙度磨具的结合强度。     

低钠刚玉磨料磨削性能研究

钠作为白刚玉磨料中一种杂质,如含量高,会生成很多β-氧化铝,影响白刚玉的性能,导致白刚玉产生结晶度降低,切削能力下降,容易粉化破碎,热稳定性低等缺陷,为了验证钠含量对白刚玉磨料性能的影响,文章采用36号普通白刚玉和低钠白刚玉为原料,制备树脂结合剂的抗折强度试样和砂轮样品,通过对磨料的单颗粒抗压强度检测,观察微观形貌,并对样品的磨削性能等力学性能进行测试,分析钠含量对磨具性能的影响。实验结果表明磨料的单颗粒抗压强度二者无明显差别,低钠白刚玉样品的抗折强度33.81MPa,普通白刚玉样品30.47MPa,提高11.16%;样品的抗冲击强度分别是2.2025kJ/m^(2)和1.9539kJ/m^(2),提高了12.7%;由砂轮的磨削实验结果可知,低钠白刚玉砂轮的磨削性能比普通白刚玉砂轮磨削性能提高了51.1%,低钠白刚玉砂轮力学性能和磨削性能都显著高于普通白刚玉砂轮。     

纳米氮化钒对cBN磨具用陶瓷结合剂性能的影响

以硼铝硅酸盐为基础体系,通过将不同含量的纳米氮化钒加入到基础陶瓷结合剂中,制得纳米陶瓷结合剂试样条。采用万能试验机、金相显微镜和差热分析仪(TG-DSC)等仪器对所得试样的抗折强度、断口形貌和热重损失等进行分析。重点分析不同含量的纳米VN对陶瓷结合剂的力学性能和微观结构影响。结果表明:基础结合剂在650℃进行烧成时抗折强度是11.75 Mpa;在陶瓷结合剂中加入6%纳米氮化钒时,陶瓷结合剂的性能最好,其中抗折强度为47.59 Mpa,流动性为174%。     

玻璃涂覆CBN磨料的制备及其应用

采用溶胶凝胶法制备了SiO2-Al2 O3-Na2 O基玻璃涂层CBN磨料,通过扫描电子显微镜(SEM)、X射线能谱仪(EDS)、热膨胀仪及力学性能测试仪表征了玻璃涂层CBN磨料的性能,并将玻璃涂层CBN磨料应用于陶瓷结合剂磨具.实验结果表明:SiO2-Al2 O3-Na2 O基涂层玻璃的热膨胀系数与CBN磨料相匹配,对CBN颗粒形成良好的包裹润湿.玻璃涂层的CBN磨料单颗粒抗压强度和冲击韧性均比未涂层的磨料有所提高.在陶瓷结合剂CBN磨具中玻璃改性增强了CBN磨料与结合剂的界面区结合,提高了磨料与陶瓷结合剂之间的粘结力.     

用陶瓷cBN砂轮磨削LED基板

为提高LED基板的磨削效果,研究了结合剂成分及造孔剂形态和粒度对cBN陶瓷砂轮磨削性能的影响;通过调整陶瓷结合剂中成分的比例,使cBN砂轮的性能得到了不同程度的提高。实验结果表明:采用不同结合剂、同粒度同比例造孔剂,结合剂耐火度范围为800℃～865℃,流动性为140%～190%,抗折强度由85.21 MPa提高到92.37 MPa,抗拉强度由18.69 MPa提高到19.34 MPa;采用不同结合剂、不同粒度同比例造孔剂,结合剂耐火度范围为820℃～865℃,流动性为140%～160%,抗折强度由62.26 MPa提高到102.25 MPa,抗拉强度由16.46 MPa提高到20.38 MPa。     

Preparation and characterization of vitrified CeO2 coated cBN composites

The performances of vitrified cBN composites are deeply affected by the wettability of vitrified bonds on cBN particles. CeO₂ coated cBN particles were successfully prepared for the further improvement of the covering and wetting of cBN by vitrified bonds. The microstructure and properties of vitrified cBN composites were characterized by scanning electron microscope (SEM), hot stage microscope (HSM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and flexural strength. Results showed that the prepared CeO₂ coating on the surface of cBN was uniform and dense. Besides, the improved wettability of vitrified bonds on CeO₂ coated cBN particles accompanied with the formation of Ce–O–Al and N–Si confirmed by XPS were supposed to conduce to enhancing the holding power of the vitrified bonds to cBN particles, which resulted in increasing the flexural strength of vitrified cBN composites by 9.16%. Thus, coating cBN with CeO₂ was a potential and effective method to obtain vitrified cBN composites with higher flexural strength.     

Self-sharpening property of porous metal-bonded aggregated cBN wheels during the grinding of Ti–6Al–4V alloys

Grinding process with cubic boron nitride (cBN) superabrasive wheels has been the subject of extensive research during high efficiency and precision machining difficult-to-cut materials in aerospace and aviation industries. However, the grinding performance and tool-life of conventional cBN abrasive wheels are severely affected by the probable macro-fracture and pull-out of cBN grains owing to their anisotropic crystalline structure. In this case, porous metal-bonded grinding wheels coupled with high-performance aggregated cBN abrasive grains were developed to improve tool performance and machined surface integrity. Characterisation of morphologies, including as-sintered aggregated cBN abrasive grains, pore structures and grain wear evolutions, was performed. The grinding ratio, grinding forces, force ratio and ground surface roughness were evaluated through single-grain grinding of Ti–6Al–4V alloys. Experimental results indicated that the porous aggregated cBN wheels had abundant chip storage space and excellent wear resistance. A stable grinding force ratio and small ground surface roughness were obtained during the tool wear tests due to the combined characteristics of microfracture and partial macrofracture of multi-layer cBN particles.     

Wear characteristics of single-layer cBN abrasive tools using ultrasonic vibration–assisted induction brazing techniques

Single-layer brazed superhard abrasive tools have been widely employed in grinding of difficult-to-machine materials in aerospace, aiming at the improvement of the grinding performance and quality. However, the chemical metallurgical reaction during conventional induction brazing (CIB) is severe, and the brazing quality is poor, resulting in a rapid wear and thus reducing service life of abrasive tools. In this case, the single-layer brazed cBN abrasive tools were fabricated using ultrasonic vibration-assisted induction brazing (UVAIB) technology, and the wear comparative experiments of Ti–6Al–4V alloys was carried out using UVAIB and CIB abrasive tools. Results indicate that compared to the CIB abrasive tool, the UVAIB abrasive tool has the higher average exposure height of abrasive grains, lower grinding forces and more stable grinding force ratio during wear processes. Meanwhile, the UVAIB abrasive tool has a slowly decreased exposure height of abrasive grains, a superior wear state and low proportion of macro-fracture as the material removal volume raises. In addition, UVAIB abrasive tool possesses micro-cracks at the top of abrasive grains, leading to micro-fractures of abrasive grains to improve the self-sharpening ability and grinding performance.     

切削刀具用立方氮化硼涂层的研究进展

立方氮化硼( cubic boron nitride,cBN)具有优异的物理力学性能和极高的化学稳定性,可以胜任铁系金属的加工,在高性能切削刀具等领域有着广泛的应用前景.cBN涂层在复杂刀具应用中有着不可替代的作用,由于气相生长高纯度和结合性能的cBN刀具涂层仍存在着较多的技术难题,因此仍然难以得到广泛的应用.本文综述了近20年来气相沉积cBN涂层的研究进展,阐述了物理气相沉积与化学气相沉积cBN涂层的方法与机理,分析了cBN刀具涂层制备与应用的关键问题,结合研究现状指出了cBN刀具涂层研究的发展方向.     

Influence of TiO2 on the physical properties of low-temperature ceramic vitrified bond and mechanical properties of CBN composites

The microstructures and properties of vitrified bond abrasive tools made of CBN grains and advanced vitrified bond systems with different TiO₂ doping amounts were investigated. Based on the experimental observations and analysis, the incorporation of TiO₂ in appropriate amount (4 wt.%) was beneficial to the improvement on flowing ability and thermal expansion property of the vitrified bond systems, and mechanical properties of the CBN composites including bending strength and Rockwell hardness were obviously improved. On the basis of discussion for microstructure, the CBN grains were better covered by vitrified bond and acquired less pores when the content of TiO₂ reached 4 wt.%. These results were related to the role of TiO₂ in the glass network structure which was analyzed by Fourier transform infrared spectroscopy (FTIR).     

Effects of Ni addition on properties of vitrified bond CBN composites in strong magnetic field

Properties of vitrified bond with varying Ni doping amounts were extensively investigated. Effects of Ni addition on microstructures and properties of vitrified bond cubic boron nitride (CBN) composites prepared in strong magnetic field were investigated for applications in CBN grinding tools. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction and other methods. The refractoriness, fluidity, and bending strength of vitrified bond were evaluated. Bending strengths, microstructures, and phase compositions of vitrified bond CBN composites achieved using conventional and strong electromagnetic sintering techniques were compared. Results show that the addition of Ni to vitrified bond CBN composites improved the fluidity and bending strength of the vitrified bond. Strong electromagnetic sintering improved the mechanical strength and pore structure of vitrified bond CBN composites. Moreover, the introduction of the strong magnetic field facilitated Ni migration and aggregation in vitrified bond, rotated abrasives, and formed new substances, thus increasing the stability of vitrified bond CBN composite thermal material. Also, strong magnetic field inhibit grain growth of non-magnetic and ferromagnetic materials with fine-grain effect.     

Effects of sintering in a high magnetic field on properties of vitrified bond and vitrified CBN composites

Vitrified bond CBN grinding wheels are being widely used due to their superior performance. Also, advantages of vitrified grinding wheels are high elastic modulus, stable chemical property, and low thermal expansion coefficient. Brittleness and low strength are key factors restricting the development of vitrified bond CBN grinding wheels. In this paper, the sintering in a high magnetic field was innovatively introduced into the manufacturing of vitrified bond CBN grinding wheels, and the effects of sintering in a high magnetic field on properties on vitrified bond and vitrified CBN composites were systematically investigated. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction. It was observed that microstructure of vitrified bond could be changed, grain orientation could be controlled and average grain size could be decreased in a high magnetic field, while vitrified bond strength could be simultaneously improved. High quality vitrified bond could be obtained by appropriately adjusting the strength and direction of high magnetic field. Results demonstrated that vitrified bond properties were improved when the magnetic field strength was 6?T. In order to highlight the high magnetic field effect on the vitrified CBN composites, the ordinary CBN abrasives and nickel plated CBN abrasives were used respectively. Microstructures, bending strengths of vitrified CBN composites were compared in different high magnetic fields. When the magnetic field strength was appropriate (less than 6?T), the binding characteristic of vitrified bond CBN composites with nickel plated CBN abrasives was greatly improved. The highest bending strength value of vitrified CBN composites was 79.5?MPa in 6?T high magnetic field.     

Effects of open pores on grinding performance of porous metal-bonded aggregated cBN wheels during grinding Ti–6Al–4V alloys

Porous metal-bonded wheels coupled with the aggregated cubic boron nitride (cBN) grains and water-soluble carbamide particles as pore-forming agents were fabricated, aiming to the improvement of grinding wheel performance and ground surface quality in grinding of Ti–6Al–4V alloys. Grinding forces and force ratio, ground surface roughness and microhardness were investigated to evaluate wheel performance. In addition, the wear evolutions of cBN grains and macropores were performed as the material removal volume increases during wheel wear tests. Findings show that the dynamic changing behavior of the coverage and exposure of open pores attributes to the improvement of grinding performance and ground surface quality of porous AcBN wheels. Meanwhile, the promising self-sharpening property of wheels can be guaranteed in basis of dynamic wear variations of multiple cBN abrasive grains layer by layer.     

氧化铁涂衣磨料性能的实验研究

实验研究了氧化铁涂衣磨料与未涂衣磨料的单颗粒抗压强度和亲水性;对分别用它们制成的涂附磨具(砂布)的磨削性能进行了对比实验.证明了涂衣磨料的性能明显的优于未涂衣磨料,用涂衣磨料制成的涂附磨具的磨削性能好,使用寿命长,较显著地提高了磨具的质量,具有推广应用的价值.     

The effect of metal coatings on the interfacial bonding strength of ceramics to copper in sintered Cu-SiC composites

Cu-SiC composites are very promising materials which have high thermal and electrical conductivity and may find many applications. Unfortunately, the main disadvantage of these materials is the dissolution of silicon in copper at elevated temperature, which significantly reduces their properties. In order to overcome this problem particles can be coated with a protective material before sintering. In this paper– the influence of three different metallic coatings on bonding strength were investigated. SiC particles were coated with tungsten, chromium or titanium. As reference a material with uncoated particles was prepared. The experiments were carried out with the use of microtensile tester. The highest increase in strength was observed in the case of chromium coating. On the other hand, the titanium coating, which was of very poor quality, decrease the bonding strength in comparison with uncoated particles. Furthermore, scanning electron and optical microscopes were used to determine the mechanism of debonding.