New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.

Study on iron-based diamond bit by DC-electroplating method

Iron-plating technology used for restoration of axis parts was applied to the manufacture of diamond bits in this paper.The technology for electroplating diamond bit of iron matrix was mastered through repeated experiments and research.The productive practice indicated that the DC-electroplated iron matrix of diamond bit has high hardness and good diamond exposure ability;the drilling rate of electroplated iron-based diamond bit was 2 m/h when drilling in grade 9 granite and bit life can reach 44 m,which can satisfy the drilling production requirements.

Approach for Polishing Diamond Coated Complicated Cutting Tool: Abrasive Flow Machining(AFM)

Lower surface roughness and sharper cutting edge are beneficial for improving the machining quality of the cut?ting tool, while coatings often deteriorate them. Focusing on the diamond coated WC?Co milling cutter, the abrasive flow machining(AFM) is selected for reducing the surface roughness and sharpening the cutting edge. Comparative cutting tests are conducted on di erent types of coated cutters before and after AFM, as well as uncoated WC?Co one, demonstrating that the boron?doped microcrystalline and undoped fine?grained composite diamond coated cutter after the AFM(AFM?BDM?UFGCD) is a good choice for the finish milling of the 6063 Al alloy in the present case, because it shows favorable machining quality close to the uncoated one, but much prolonged tool lifetime. Besides, compared with the micro?sized diamond films, it is much more convenient and e cient to finish the BDM?UFGCD coated cutter covered by nano?sized diamond grains, and resharpen its cutting edge by the AFM, owing to the lower initial surface roughness and hardness. Moreover, the boron incorporation and micro?sized grains in the underly?ing layer can enhance the film?substrate adhesion, avoid the rapid film removal in the machining process, and thus maximize the tool life(1040 m, four times more than the uncoated one). In general, the AFM is firstly proposed and discussed for post?processing the diamond coated complicated cutting tools, which is proved to be feasible for improving the cutting performance

Study on Abrasion Resistance Anisotropy of Natural Diamond Crystals

This paper studies the abrasion mechanism of natural diamond crystals,proposes a new theory on soft and hard directions to grind diamonds in different planes.Examination of the micro-structure of polished surface by SEM shows diamond is mainly removed through a micro-cleavage process in (111) planes and the abrasion resistance of diamond relates to the orientation of cleavage planes,and the abrasion resistance anisotropy of diamond crystals is mainly due to the different levels of difficulty in micro-cleavage,while they are lapped in different directions.The results of analysis are in conformance with experimental results.

Direct Deposition of Polycrystalline Diamond Films on the Si(100) Mirror Surface by Hot Filament Chemical Vapor Deposition

High quality diamond films have been deposited on Si(100) mirror surface without using any surface pretreatment such as abrasive diamond scratching,diamond-like carbon predeposition or oil treatment.The experiments are carried out in the hot filament chemical vapour deposition system by using the mixture of methane,hydrogen and oxygen.The films show the well-defined facets and are confirmed by Raman spectroscopy and scanning electron microscopy to be high quality diamond films.In this deposition process,higher substrate temperature,high filament temperature and oxygen addition play the important roles in diamond nucleation on the mirror-smooth Si(100) surface.

Study on precision dicing process of SiC wafer with diamond dicing blades

An innovative method for high-speed micro-dicing of SiC has been proposed using two types of diamond dicing blades,a resin-bonded dicing blade and a metal-bonded dicing blade.The experimental research investigated the radial wear of the dicing blade,the maximum spindle current,the surface morphology of the SiC die,the number of chips longer than 10μm,and the chipped area,which depend on the dicing process parameters such as spindle speed,feed speed,and cutting depth.The chipping fractures in the SiC had obvious brittle fracture characteristics.The performance of the metal-bonded dicing blade was inferior to that of the resin-bonded dicing blade.The cutting depth has the greatest influence on the radial wear of the dicing blade,the maximum spindle current,and the damage to the SiC wafer.The next most important parameter is the feed speed.The parameter with the least influence is the spindle speed.The main factor affecting the dicing quality is blade vibration caused by spindle vibration.The optimal SiC dicing was for a resin-bonded dicing blade with a spindle speed of 20000 rpm,a feed speed of 4 mm/s,and a cutting depth of 0.1 mm.To improve dicing quality and tool performance,spindle vibrations should be reduced.This approach may enable high-speed dicing of SiC wafers with less dicing damage.

孕镶金刚石钻头磨损机理研究

孕镶金刚石钻头通过钻头胎体的持续磨损实现金刚石的自锐和高效破岩。因此,研究金刚石钻头磨损的影响因素及其影响程度和影响机理,对孕镶金刚石钻头的设计和使用非常重要。本次研究探讨了岩石物理力学性质、钻头胎体性能和钻进工艺参数等因素对孕镶金刚石钻头磨损过程和磨损机理的影响。分析表明,对钻头磨损最为显著的影响因素是岩石中的硬质颗粒导致的磨粒磨损,其次是钻头胎体与岩粉之间的粘着磨损,以及冲洗液中岩粉颗粒导致的冲蚀磨损。在此基础上,以不同硬度的钻头胎体摩擦磨损试验结果为例,探讨了钻头胎体性能及其内部硬质点对钻头磨损的影响机理。该研究成果可为科学设计与合理使用孕镶金刚石钻头提供依据。

陶瓷结合剂金刚石团聚磨料探索

细粒度金刚石微粉大量积压是目前金刚石微粉制造行业面临的问题之一,为促进其应用,以铝硼硅结合剂为黏接剂、Si粉和Ti粉为添加剂制造团聚磨料试样,并将制成的团聚磨料加入铝硼硅结合剂中制成陶瓷结合剂试样,对所制试样的抗弯强度、物相构成和微观形貌进行分析。结果表明:添加Si或Ti的铝硼硅黏结剂均能起到团聚金刚石的作用;当团聚磨料中Si或Ti的质量分数为10.0%时,所制得的陶瓷结合剂试样抗弯强度最大,且添加Si的团聚磨料试样抗弯强度为43.74 MPa;当Si或Ti的质量分数超过10.0%时,团聚磨料试样中出现大量Si或者TiO2峰,其抗弯强度急剧下降;添加Si的团聚磨料试样与添加Ti的团聚磨料试样相比,其具有更大的粒度和更均匀的粒度分布,添加Si的铝硼硅黏结剂可将1~2μm的磨料团聚为5~10μm的磨料。

不烧滑板磨削加工用Fe-Ni-Cu-Sn金属基金刚石工具的制备与性能

Al_(2)O_(3)-C不烧滑板作为连铸功能耐火材料在炼钢领域中受到广泛应用,而金属结合剂金刚石工具在滑板磨削加工中起到关键作用。本工作通过热压烧结法制备Fe-Ni-Cu-Sn金属基胎体和Fe-Ni-Cu-Sn金属基金刚石工具,首先研究烧结温度、保温时间和烧结压力对金刚石工具胎体力学性能的影响,获得优化的胎体烧结工艺参数并为后续制备金刚石工具奠定基础;其次研究不同的金刚石磨料对金刚石工具力学性能及磨削不烧滑板性能的影响,通过研究金刚石的浓度、粒度、品级与加工工具磨削效率、寿命及锋利度的关系,从而得到磨削加工不烧滑板的金刚石工具中金刚石磨料的优化参数,通过SEM对金刚石工具表面胎体与金刚石磨料的结合状态、金刚石的磨损情况进行表征。实验结果表明:金刚石工具胎体的最佳烧结工艺参数是烧结温度、烧结压力和保温时间分别为785℃、170 MPa、240 s;金刚石工具中的金刚石磨料最优选择为金刚石浓度25%、粒度45/50、品级SMD35。

金刚石砂轮盘轮廓精度检测及盘面精密修整方法

金刚石砂轮盘的轮廓精度检测及盘面精密修整是金刚石刀具制造领域的关键问题。首先为实现砂轮盘轮廓误差的高精度测量,提出一种基于激光三角测量的在位测量方法,实现了砂轮盘面误差亚微米级精度的高效检测。实验结果表明,该方法可以方便地评估不同精修参数下的修整精度。随后,采用单点金刚石修整法对青铜基金刚石砂轮盘进行了盘面精密修整工艺实验,分别探究了修整进给深度、主轴转速、主轴往复运动频率以及修整压力对盘面修整精度的影响,并优选了修整工艺参数,优选的工艺参数为:修整深度1µm,主轴转速3000r/min,主轴往复频率0.15Hz,接触压力14.7N。最后,不同修整精度的砂轮盘分别被用于研磨金刚石微楔形刀具。实验结果表明,所提出的砂轮盘精度检测和盘面精密修整方法对提高金刚石刀具的制造质量具有重要应用价值。

单颗金刚石磨粒划擦2D SiC_(f)/SiC复合材料实验

为了揭示2D SiC_(f)/SiC复合材料的磨削去除机理,根据2D SiC_(f)/SiC复合材料的编织结构特点,分别在2D SiC_(f)/SiC纤维的编织表面(woven surface,WS)和叠加表面(stacking surface,SS)沿0°、45°和90°方向开展单颗金刚石磨粒划擦实验,测量其划擦力和划痕深度,并观察划痕表面形貌。结果表明:在WS0(纤维编织表面的0°方向)上SiC_(f)/SiC材料的去除方式主要为纵向纤维(纤维轴向与进给速度方向一致)的剪切、拉伸、弯曲断裂和横向纤维(纤维轴向与进给速度方向垂直)的剪切、弯曲断裂;在WS45(纤维编织表面的45°方向)上主要为纤维的剪切、弯曲、拉伸断裂;在SS0(纤维叠加表面的0°方向)上主要为法向纤维(纤维轴向垂直于划擦表面)的延性去除、剪切、弯曲断裂,纵向纤维的剪切、拉伸、弯曲断裂;在SS90(纤维叠加表面的90°方向)上主要为法向纤维的延性去除、剪切、弯曲断裂和横向纤维的剪切、弯曲、拉伸断裂。由于SiC纤维的各向异性,不同方向、不同断裂形式有不同的力学性能,剪切断裂所需要的力最小,拉伸断裂所需要的力最大。在相同划擦深度下,因WS0、WS45、SS0、SS90方向上断裂形式的不同和剪切、弯曲、拉伸断裂所占的比例不同,其划擦力大小依次为FSS0>FWS45>FSS90>FWS0。且磨粒切入复合材料后随着裂纹的扩展和相互贯通,SiC基体会一起被剥离去除,部分基体受到挤压去除后再次被磨粒划擦去除形成延性划痕。2D SiC_(f)/SiC复合材料切削时宜选择WS0方向,而尽量避开SS0方向。

辅助磨料对树脂结合剂金刚石砂轮性能的影响

采用绿色碳化硅、黑色碳化硅和碳化硼三种不同的辅助磨料,通过同一配方和生产工艺制成树脂结合剂金刚石砂轮,研究了辅助磨料对其性能的影响。结果表明:绿色碳化硅和黑色碳化硅在增加砂轮强度方面的作用高于碳化硼;碳化硼能提高砂轮的耐磨性和锋利度,可以作为配方设计的参考辅助磨料。

磨粒几何排列对Inconel 718磨抛的有限元仿真研究

目的为了提高砂带磨抛镍基合金Inconel 718的表面精度,避免砂带上磨屑堆积等问题,针对砂带表面磨粒的顶端结构以及排列方式进行了分析,通过三维动力学仿真方法,研究磨抛过程中磨削力和磨屑的变化情况。方法开展三种尖端类型磨粒和排列间距、倾角对Inconel 718的磨削机理研究,先分析尖端为点型、线型、面型的磨粒磨削过程,对比不同尖端类型磨粒的切屑形态与磨削力的大小,根据挑选出的点型尖端磨粒建立正四面体磨粒,利用该类型磨粒建立有序与无序的金刚石多磨粒模型,通过有限元软件分析磨粒水平和竖直方向上的间隙大小以及磨粒排布线倾角变化对磨削力和工件表面质量的影响。结果发现点型尖端磨粒产生的切屑呈碎屑状,更容易在多磨粒间排出,不易堵塞砂带,且在磨削过程中所受的磨削力更小;分析发现有序排列的磨粒类型具有很大的优势,能够提高工件表面精度,在工件表面产生大小均匀的沟槽,同时降低砂带受到的磨抛力小;发现磨削力大小会随着排布线倾角的增加呈现先增大后减小趋势。通过与实验对比,发现磨屑的形状会随着水平方向间隙的增大而变化,呈现出由块状至带状到细长条状的变化规律,细长条状的磨屑更易从间隙中排出,从而达到降低磨抛力的效果。结论采用点型尖端磨粒和合适的磨粒排布规律能够有效提高磨抛后的工件表面精度和促进磨屑的排出,为砂带的制造生产提供新的思路。

一种树脂金刚石复合材料的分子动力学模拟

本文研究一种用于制备微细砂轮的树脂金刚石复合材料,该复合材料由丙烯腈-丁二烯-苯乙烯(ABS)作为基体,聚氯乙烯(PVC)作为混料,邻苯二甲酸二辛酯(DOP)作为加工助剂,与金刚石磨粒混合而成。对5种不同配比的共混体系进行分子动力学模拟,结果显示:提高ABS的质量比,复合材料分子间作用力逐渐增强,密度逐渐降低,延展性和柔性先减小后增加,ABS和PVC的相容性先减小后增加,复合材料最佳配比为62.5wt%ABS、18.6wt%PVC、8.3wt%DOP和10.6wt%金刚石磨粒。

影响PDC磨耗比测试的关键因素研究

以PDC磨耗比测试过程中称量和磨削环节为研究对象,细化PDC称量,探讨PDC放置位置和有无隔磁对PDC称量稳定性的影响,研究PDC磨削位置、磨削角度以及磨削时间对其磨耗比的影响。结果表明:PDC的磁性是影响其称量稳定性的关键因素,木隔片可有效降低PDC称量误差。PDC对称位置的磨耗比相对偏差仅为1.8%~2.0%,但PDC在135°磨削的磨耗比是其在45°磨削的1.3~2.8倍,PDC的磨耗比随着磨削时间的增加而下降,且最大降幅达到了18.3%。

Ni-Cr合金真空单层钎焊金刚石砂轮

单层高温钎焊超硬磨料砂轮具有传统电镀砂轮无法比拟的优异磨削性能 ,国内应及早研制开发应用此种砂轮。本文利用真空炉中钎焊的方法 ,用Ni Cr合金钎料 ,适当控制钎焊温度、保温时间和冷却速度 ,实现了金刚石与钢基体间的高强度连接。扫描电镜X射线能谱 ,结合金相及试样逐层的X射线结构分析 ,剖析了Ni Cr合金与金刚石和钢基体钎焊界面的微区组织结构 ;揭示了Ni Cr合金对金刚石和钢基体表面的浸润和钎焊机理。即在钎焊过程中会在金刚石界面形成富Cr层并与金刚石表面的C元素反应生成Cr7C3,在钢基体结合界面上Ni Cr合金和钢基体中的元素相互扩散形成冶金结合 ,这是实现合金层与金刚石和钢基体都有高结合强度的主要因素。最后重负荷磨削试验表明金刚石为正常磨损 ,没有整颗金刚石脱落 。

Ti对陶瓷结合剂及金刚石磨具性能的影响

探讨了Ti的加入对R2O-B2O3-Al2O3-SiO2系陶瓷结合剂及金刚石磨具性能的影响。通过耐火锥法、平面流淌法、扫描电镜和能谱分析、三点弯曲法、洛氏硬度计等测试手段,测定了Ti对陶瓷结合剂的耐火度、流动性以及对金刚石磨具的微观结构、抗折强度、硬度等性能的影响。结果表明:Ti的加入使结合剂熔融温度降低,线膨胀系数随Ti含量的增加而增加;Ti的加入使陶瓷结合剂金刚石磨具的气孔率降低、致密度提高,改善了结合剂对金刚石的润湿性;添加15%Ti的结合剂制得的金刚石磨具在780℃烧成时抗折强度最高,达到49.86 MPa,硬度达到76.27 HRB,与未加Ti的陶瓷结合剂金刚石磨具相比,强度提高41.2%,硬度提高44.92%。

Ni-Cr合金与金刚石和钢基体界面微区的分析研究

利用扫描电镜 X射线能谱 ,结合金相及试样逐层的 X射线结构分析 ,剖析了 Ni-Cr合金与金刚石和钢基体钎焊界面的微区组织结构 ;揭示了 Ni-Cr合金对金刚石和钢基体表面的浸润和钎焊机理。即在钎焊过程中 ,Ni-Cr合金中的 Cr元素分离出在金刚石界面形成富 Cr层并与金刚石表面的 C元素反应生成 Cr7C3,在钢基体结合界面上 Ni-Cr合金和钢基体中的元素相互扩散形成冶金结合 ,这是实现合金层与金刚石和钢基体都有较高结合强度的主要因素。

Ni对金刚石磨具陶瓷结合剂性能的影响

采用粉末冶金法制备了不同Ni含量的金刚石磨具陶瓷结合剂。通过SEM、EDS、XRD、TG-DSC、三点弯曲等分析方法对含Ni陶瓷结合剂的微观结构、结合界面、氧化性能以及抗折强度等性能进行分析,同时研究了含Ni陶瓷结合剂对金刚石润湿性的影响。结果表明,在实验范围内,Ni的加入对陶瓷结合剂耐火度及流动性影响不大,但降低了结合剂的烧成收缩;750℃烧成时,Ni与陶瓷结合剂界面结合紧密,界面形成合金化结合,提高了结合强度,抗折强度随着Ni的加入量先升高后降低,当Ni含量为15%(质量分数,下同)时达到最大值62.8MPa,较基础陶瓷结合剂提高了19.41%;Ni的加入能够改善高温状态下陶瓷结合剂对金刚石的润湿性,当Ni添加量为15%时,陶瓷结合剂对金刚石的润湿角为64°,比未添加Ni时的润湿角(84.5°)减小了24.3%。

加Cr银基钎料钎焊单层金刚石砂轮的实验研究

概述了单层高温钎焊超硬磨粉砂轮的工艺优势，这种新型超硬磨料砂轮以其卓越的磨削性能在今后逐步替代传统电镀砂轮应是一种无法抗拒的必然趋势．鉴于它极其广阔的应用前景，国内在推广应用超硬磨料砂轮时也必将大力开发此种单层钎焊砂轮。文中利用高频感应钎焊的方法，用添加有Ｃｒ的Ａｇ－Ｃｕ合金做中间层材料，在一定的钎焊温度和时间下，实现了金刚石与钢基体间的牢固连接．经Ｘ射线能谱及Ｘ射线衍射分析发现Ｃｒ与金刚石之间形成Ｃｒ３Ｃ２，与钢基体之间形成（ＦｅxＣｒｙ）Ｃ，这是实现合金层与金刚石及钢基体之间都有较高结合强度的主要因素。最后通过磨削实验证实了金刚石确实有较高的把持强度。