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.     

Effect of TiO2 addition and high magnetic field sintering on properties of vitrified bond CBN composites

Vitrified bond CBN composites, with different amounts of TiO₂ doping, were prepared by conventional sintering and high magnetic field sintering processes. Mechanical properties, cross-sectional morphology, refractoriness, fluidity and structural characterization have been carried out to understand the role of TiO₂ addition and sintering conditions. Results show that TiO₂ addition significantly affected bending strength, refractoriness and fluidity of vitrified bonds. In addition, high magnetic field sintering improved bending strength and the microstructure of vitrified bond CBN composites. Due to high magnetic field sintering, CBN grains were completely covered by vitrified bond and exhibited fewer pores. In addition, high magnetic field promoted the growth of specific grains, such as SiO₂, whereas suppressed grain growth of other crystal phases, such as NaAlSi₃O₈.     

Preparation of a novel vitrified bond CBN grinding wheel and study on the grinding performance

The vitrified bond CBN grinding wheels are characterized by high efficiency, high precision, and low environmental pollution. In recent years, the vitrified bond CBN grinding wheel has been widely used in manufacturing industries such as aerospace, automotive, and machine tools. In this study, a novel vitrified bond formulation containing nano SiO₂ and nano CeO₂ is selected to prepare the grinding wheel. The grinding experiments on 45# steel and YG20 alloy indicate that the grinding performance of the nano vitrified bond grinding wheel is significantly better than that of the conventional vitrified bond grinding wheel. The introduction of nano SiO₂ and nano CeO₂ greatly improves the machining performance of the vitrified bond CBN grinding wheel.     

Fabrication of porous structure vitrified bond diamond grinding wheel via direct ink writing

Porous vitrified bond grinding wheels with complex structure, high porosity, controllable pore size have fundamental application in high efficiency and precision grinding of hard and brittle materials. In this paper, direct ink writing (DIW) is proposed to fabricate three kinds of grinding wheels, including solid structure, triangle structure, and lattice structure. Moreover, the rheological property of ceramic ink with different doses of xanthan gum (XG) solution was investigated to ensure printability, demonstrating 3% XG solution can meet requirements. Additionally, the effect of sintering temperature and pore former (PMMA) contents on size shrinkage rate, morphology, mechanical strength, and porosity et al. were studied. The results indicate that the diamond grinding wheel with 30 vol% PMMA and sintered at 670 °C possess the best comprehensive performance. Besides, grinding performance was evaluated by surface morphology, surface roughness, and material removal rate. Among the DIW-fabricated wheels, triangle structure grinding wheel and lattice structure grinding wheel possess a higher material removal rate than solid structure grinding wheel. Therefore, the porous structure grinding wheels fabricated by DIW present the advantage of controllable porosity, excellent self-sharpening ability, and higher bond strength, which may pave the way for designing a new generation vitrified bond diamond grinding wheel.     

Variations in structure and properties of vitrified bonds and vitrified diamond composites prepared by sol-gel and melting methods at different sintering temperature

Differences in structure and properties of Na₂O–Al₂O₃–B₂O₃–SiO₂ vitrified bonds and vitrified diamond composites prepared by sol-gel and melting methods were methodically discussed. Results showed that the vitrified bond prepared by sol-gel method contained more [AlO₄] tetrahedron and owned higher bending strength, with the maximum value reaching 137 MPa, 31.73% higher than that prepared by melting method (104 MPa). As the sintered temperature rose, coefficient of thermal expansion of the vitrified bond prepared by sol-gel method increased first and then decreased, acquiring a maximum value of 5.75 × 10⁻⁶ °C ⁻¹ at 720 °C, which was still much lower than the minimum value of vitrified bond prepared by melting method (7.02 × 10⁻⁶ °C ⁻¹). The vitrified diamond composite prepared by sol-gel method possessed lower sintering shrinkage than that prepared by melting method, and could be applicable to the production of grinding tools with high dimensional accuracy. What's more, the maximum bending strength of vitrified diamond composites obtained by sol-gel method was 106 MPa, 24.7% higher than that of vitrified diamond composites prepared by melting method (85 MPa).     

Effect of polycrystalline mullite fibers on the properties of vitrified bond and vitrified CBN composites

The effect of polycrystalline mullite fibers (PMFs) on the properties of vitreous bonds and vitrified CBN composites was investigated. The results show that the addition of PMFs can increase the porosity of composites and reduce the fluidity of binders. The vitrified composites incorporating 6.4 wt% PMFs display excellent mechanical strength, which is enhanced by 21.2% compared with that of composites without PMFs sintered at the optimal sintering temperature. Meanwhile the thermal expansion coefficient of vitrified bond reduces from 6.256×10⁻⁶ °C⁻¹ to 4.805×10⁻⁶ °C⁻¹ with increasing fraction of PMFs. The improvement of mechanical strength is associated with the change of cracking mechanisms of the composites with fibrous crystals and the existence of several observed mechanisms, including fiber pull-out, fiber bridging and rupture.     

Effect of porosity on the grinding performance of vitrified bond diamond wheels for grinding PCD blades

In this paper, the preparation of nano-AlN modified Na₂O–B₂O₃–SiO₂ vitrified bond diamond tools with various porosities is reported. The effects of porosity on the impact strength and grinding properties of the wheels for grinding PCD blades are also discussed. The results show that the porosity not only affects the impact strength of the wheels but also the grinding properties, such as the grinding efficiency, the self-dressing, the service life and the surface roughness of the work pieces. The optimum porosity for nano-AlN modified Na₂O–B₂O₃–SiO₂ vitrified bond diamond wheels for grinding PCD tools is approximately 40.5 vol%.     

Effects of Y2O3 addition on structure and properties of LZAS vitrified bond for CBN grinding tools application

The effects of Y₂O₃ addition on the structure and properties of Li₂O–ZnO–Al₂O₃–SiO₂ (LZAS) vitrified bonds were firstly investigated for CBN grinding tools application. Glasses and glass-ceramics were characterized using differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy and infrared spectroscopy. The thermal expansion coefficient (TEC), microhardness, bending strength and chemical durability of the obtained products were also evaluated. Results showed that Y₂O₃ acted as the network former in the track of SiO₄ tetrahedrals. Introducing Y₂O₃ in the glasses increased the glass transition temperature and crystallization temperature. The crystallization of the main β-quartz_ss phase increased with increase of Y₂O₃ content. The morphology of the crystals was dependent on the Y₂O₃ content. The TEC (5.15×10⁻⁶/°C) of vitrified bond containing 1.0 mol% Y₂O₃ (Y1.0) was very close to the TEC (5.0×10⁻⁶/°C) of CBN grains. Moreover, Y1.0 vitrified bond exhibits a high microhardness (5.98 GPa), a high bending strength (202 MPa) and a good chemical durability (20 days, DR=2.8×10⁻⁹ g/cm² min), suggesting that it would be a promising material for CBN grinding tool.     

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).     

Influence of TiO2 amount on the interfacial wettability and relevant properties of vitrified bond CBN composites

The influence of TiO₂ amount on the microstructure and relevant properties of SiO₂-Al₂O₃-B₂O₃-Na₂O-Li₂O-BaO vitrified bond and vitrified bond CBN composites were systematically studied via SEM, EDS, FTIR, and XPS. Results indicated that adding TiO₂ could regulate the quantity of β-quartz solid solution and rutile crystals in the vitrified bond and considerably affect the thermal properties and mechanical strength of this bond. Under sintering temperature, the dense B₂O₃ oxide layer on the CBN surface diffused into vitrified bond and reacted with Ti⁴⁺ enriched at the interface to form a strong chemical Ti-B bond. This reaction extensively improved the interfacial wettability between the CBN and the vitrified bond. When the TiO₂ amount was 6wt.%, the interfacial wettability significantly improved, and the wetting angle decreased from 68° to 43°. The flexure strength and hardness of the composites were 116.18 MPa and 128 HRB, which were 48.49% and 34.74% higher than those of the basic-formula composites, respectively.     

Sintering,microstructure, and mechanical properties of vitrified bond diamond composite

The demand for high-performance grinding wheels is gradually increasing due to rapid industrial development. Vitrified bond diamond composite is a versatile material for grinding wheels used in the backside grinding step of Si wafer production. However, the properties of the vitrified bond diamond composite are controlled by the characteristics of the diamond particles, the vitrified bond, and pores and are very complicated. The main objective of this study was to investigate the effects of SiO₂–Na₂O–B₂O₃–Al₂O₃–Li₂O–K₂O–CaO–MgO–ZrO₂–TiO₂–Bi₂O₃ glass powder on the sintering, microstructure, and mechanical properties of the vitrified bond diamond composite. The elemental distributions of the composite were analyzed using electron probe micro-analysis (EPMA) to clarify the diffusion behaviors of various elements during sintering.The results showed that the relative density and transverse rupture strength of the composite sintered at 620 °C were 91.7% and 126 MPa, respectively. After sintering at 680 °C, the glass powder used in this study exhibited a superior forming ability without an additional pore foaming agent. The relative density and transverse rupture strength of the composite decreased to 48.2% and 49 MPa, respectively. Moreover, the low sintering temperature of this glass powder protected the diamond particles from graphitization during sintering, as determined by X-ray diffraction and Raman spectrum. Furthermore, the EPMA results indicate that Na diffused and segregated at the interface between the diamond particles and vitrified bond, contributing to the improved bonding. The diamond particles can remain effectively bonded by the vitrified bond even after fracture.     

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.     

Investigation on preparation of composite vitrified bonding ultrafine diamond grinding wheel and machining of PcBN inserts

The grinding of polycrystalline cubic boron nitride (PcBN) is hard owing to its high hardness and superior wear-resistance capacity. Machining of PcBN tools via vitrified diamond grinding wheels with a size above 10 μm may lead to brittle fracture instead of a ductile machining because of the poor toughness of cubic boron nitride. A uniformly dispersed M0.5/1.5 diamond grinding wheel with a composite vitrified bonding was fabricated to improve the surface roughness of PcBN inserts. It is demonstrated that the preparation of composite vitrified bonding with various additions of vitrified bonding produced by the melting-quenching technique (VB-MQ) has little effect on the performance of vitrified bonding, such as bending strength, CTE and phase and achieves the uniform dispersion of M0.5/1.5 diamond as the addition of VB-MQ is no greater than 50%. Both the grinding ratios and the surface roughness of PcBN inserts are enhanced.     

金属铝粉和纳米Al2O3粉对陶瓷结合剂性能的影响

将金属铝粉、纳米Al₂O₃粉引入基础陶瓷结合剂,通过红外光谱分析陶瓷结合剂玻璃结构,X射线衍射表征其物相变化,并测试其耐火度,利用扫描电镜分析陶瓷结合剂立方氮化硼(CBN)复合材料的微观结构,并测试抗折强度,系统分析了金属铝粉、纳米Al₂O₃粉的单掺及复掺对陶瓷结合剂性能的影响。结果表明,金属铝粉使陶瓷结合剂耐火度升高,玻璃结构没有明显改变,部分铝粉转变为Al₂O₃,添加金属铝粉的陶瓷结合剂CBN复合材料抗折强度随烧结温度升高而提高。纳米Al₂O₃粉使陶瓷结合剂耐火度降低,呈玻璃相,但有少量Al₂SiO₅晶体和Li_xAl_xSi_3-xO₆晶体析出,添加纳米Al₂O₃粉的陶瓷结合剂CBN复合材料烧结温度720 ℃时出现较高抗折强度,达93.7 MPa。金属铝粉和纳米Al₂O₃粉的复掺有利于玻璃网络结构的键合,陶瓷结合剂以玻璃相为主,也有少量晶体析出,二者复掺对提高陶瓷结合剂CBN复合材料抗折强度更有优势,但烧结温度也相应升高,烧结温度740 ℃时抗折强度达最高值,为97.4 MPa。     

The mechanism investigation of ultrasonic roller dressing vitrified bonded CBN grinding wheel

To clarify the ultrasonic roller dressing mechanism of the vitrified bonded cubic boron nitride grinding wheel (V-CBN), the collision number model between the diamond dresser and CBN grits was established based on the geometric and kinematics analysis. The influence of each dressing parameter on the collision number was analyzed and discussed. The grinding experiment was performed on the bearing raceway with the dressed V-CBN grinding wheel, results obtained discovered that there was an inverse relationship between the collision number and the surface roughness and runout of the workpiece. Additionally, compared with conventional dressing, ultrasonic dressing has the advantage in improving the surface quality because it can produce more collision numbers and raise grit retention. In words, the collision number can be used to predict the dressing effect, which provides a reference for formulating an appropriate dressing process for V-CBN to improve the workpiece surface quality and production efficiency.     

陶瓷结合剂金刚石磨具用于陶瓷干磨的探索

对比了三种不同结合剂的金刚石磨边轮在陶瓷砖边棱干法磨削工序中的使用情况。实验表明,树脂结合剂磨具磨损快并易在陶瓷砖上产生黑痕,金属结合剂磨具易发生粘刀现象而且被磨陶瓷砖表面光洁度低,相比之下,在同样的工况条件下,陶瓷结合剂磨具既不产生黑痕,能得到较好的表面光洁度,又有较好的自锐性。说明陶瓷结合剂金刚石磨具比较适合于陶瓷砖干磨工序。     

Influence of holding time on the interfacial solid solution and mechanical properties of agglomerated white fused alumina abrasives

In this paper, the aging relationship between holding time and the interfacial solid solution was utilized to prepare high-performance agglomerated white fused alumina (AWA) abrasives. The influence of holding time on the interfacial solid solution and mechanical properties of AWA abrasives were systematically investigated, and the grinding performance was thoroughly analyzed. The results showed that increasing the holding time caused the Al₂O₃ to violently infiltrate the interface between the white fused alumina (WA) particles and the vitrified bond, which led to the precipitation of a large amount of β-spodumene and monoclinic celsian in the vitrified bond and transformed the simple mechanical bonds between the WA particles and the vitrified bond into stronger chemical bonds. Thus, it was possible to control the mechanical properties of the AWA abrasives by adjusting the holding time. Specifically, after sintering at 760 °C for 4h, the single particle compressive strength and impact toughness reached the maximum values of 26 N and 63%, respectively. In comparison with the WA grinding wheel, the grinding ratio of the AWA grinding wheel was increased by 17.9% and the workpiece surface roughness was reduced by 21.1%.     

Reuse of ceramic sludge in the production of vitrified clay pipes

The use of various wastes in the manufacture of different ceramic products has proved to be beneficial from both economic and environmental points of view. In the present paper, the simultaneous reuse of ceramic sludge waste (from 0% to 6.2%) and cullet (from 0% to 10%) in the production of vitrified clay pipes has been investigated. Samples were pressed at 15?MPa, dried and subsequently fired at three different temperatures (1050, 1150 and 1250?°C) and soaking times (1, 2 and 3?h). A two-level factorial design was applied to study the effect of the various parameters on the properties of fired bodies. It was concluded that an economic recipe can be prepared involving the use of 6.2% sludge (dry basis) and 5% cullet with the balance clay +?grog followed by firing the dried body at 1050?°C for one hour only. The produced fired specimens yielded bending strength exceeding the minimum requirement for any size of soil embedded pipes and for 8″ and larger concrete cradled pipes. The suggested composition makes use of an environmentally polluting waste (sludge) and broken glass waste (cullet) and involves firing for one single hour at a temperature about 200?°C lower than commonly used.     

微波烧结陶瓷结合剂金刚石砂轮研究

为了提高陶瓷结合剂金刚石砂轮的性能,采用微波烧结技术,通过一系列试验,分析了陶瓷结合剂金刚石砂轮的微波烧结温度、陶瓷结合剂含量和金刚石磨料粒度对其性能的影响。结果表明:微波烧结温度是影响陶瓷结合剂金刚石砂轮性能的最主要因素,远超其余二者;陶瓷结合剂金刚石砂轮试样的洛氏硬度和抗弯强度在740 ℃时达到极大值且气孔率较小,此时洛氏硬度为66 HRB,抗弯强度为76.5 MPa,气孔率为17.8%;由微观组织观察可知陶瓷结合剂金刚石砂轮在740 ℃时可以实现陶瓷结合剂对金刚石磨料的均匀包裹,并且气孔较少。     

3D characterization of cubic boron nitride (CBN) composites used as tool material for high precision abrasive machining processes

Cubic boron nitride (CBN) composites are widely used as cutting tool materials for high precision abrasive machining processes. They are composed of super hard CBN abrasives and a softer binder. CBN abrasives are one of the hardest materials. They are embedded in the binder which can be metallic, polymeric or ceramic. The binder supports the abrasives and offers suitable toughness. The two components are consolidated by sintering processes under high pressure and temperature. Hence, abrasive particles exhibit an irregular spatial distribution in terms of size, location and orientation. In this work, X-ray computed tomography (CT scan) is used to investigate the geometrical properties of CBN abrasives in the volume regarding quantity, dimension and shape. A three-dimensional (3D) model is generated and the CBN abrasives are correspondingly characterized. The contribution includes both detailed explanation of CT scan and 3D modeling implementation, as well as quantification analysis of the key microstructural features for CBN composites.