热压法制备Ti3SiC2陶瓷结合剂/金刚石复合材料的组织结构

以Ti、Si、C粉、金刚石磨料为原料,添加适量Al粉,采用热压法制备Ti3SiC2陶瓷结合剂/金刚石复合材料,通过X射线衍射、扫描电镜及能谱分析对该复合材料的组织结构进行观察与分析,并研究烧结温度、助熔剂 Al 含量以及金刚石浓度对复合材料的影响。结果表明,因金刚石的反应活性较差,较低温度下热压时金刚石表面未能生长出Ti3SiC2,1300℃高温下热压形成的Ti3SiC2晶粒发育良好;适量添加Al粉有助于Ti3SiC2的合成;金刚石颗粒浓度从25%增加到50%时,金刚石参与并促进Ti3SiC2的合成,Ti3SiC2含量明显增加;金刚石表面生成晶型发育良好的Ti3SiC2晶粒,实现了磨料与结合剂的化学键合,从而提高结合剂与磨料间的结合力。     

SPS工艺制备SiCp/Si3N4复相陶瓷及其力学性能的研究

使用Si3N4、SiC陶瓷微粉为原料,氧化铝(Al2O3)和氧化钇(Y2O3)为烧结助剂,通过放电等离子烧结(SPS)技术快速制备了SiC/Si3N4复相陶瓷,并研究了SiC的添加量、SPS的 烧结温度、压力和保温时间等参数对烧结试样相对密度、力学性能及显微结构的影响.结果表明,SiC颗粒补强增韧Si3N4陶瓷的最佳添加量为15%,相对与单相Si3N4陶瓷,维氏硬度提高了6.6%,断裂韧性提高了5%,抗弯强度提高了24%,样品晶粒比较均匀,SiC颗粒诱发穿晶断裂和钉扎效应提高了基体的断裂韧性.     

球磨时间对放电等离子烧结合成Ti_3SiC_2纯度的影响

本文采用原料配比为3Ti/Si/2C/0.2Al(摩尔比)的单质混合粉体为原料,进行机械合金化(MA)和随后的放电等离子烧结(SPS),以制备高纯Ti3SiC2陶瓷,研究了球磨时间对放电等离子烧结制备Ti3SiC2的影响。结果表明,机械合金化混合粉体后,粉体颗粒明显细化。球磨10h,单质混合粉体会发生化学反应,生成TiC,Ti3SiC2混合粉体。继续球磨至20h,生成物混合粉体会显著细化。球磨时间对SPS烧结合成Ti3SiC2有显著的影响。球磨10h,即反应刚刚完毕,最有利于SPS合成致密高纯的Ti3SiC2,球磨时间较短(5h),对Ti3SiC2陶瓷的烧结促进作用不显著,而反应后继续延长球磨时间至20h,会降低烧结体中Ti3SiC2的纯度。采用球磨10h的粉体为原料,经850℃放电等离子烧结可获得纯度高达96%(质量分数,下同)的Ti3SiC2疏松块体,烧结温度提高到1100℃,可获得纯度为99.3%、相对密度高达98.9%的TiSiC致密块体。     

醇–水混合溶剂凝胶注模制备SiC多孔陶瓷的工艺与性能

将SiC陶瓷粉末、醇-水混合溶剂、丙烯酰胺-亚甲基双丙烯酰胺凝胶体系以及堇青石-锂辉石复合烧结助剂配制成料浆,采用凝胶注模成型–烧结工艺制备SiC多孔陶瓷,研究烧结助剂用量和烧结温度对多孔SiC陶瓷的形貌与显微结构、物相组成以及强度、孔径、开孔率与渗透率等性能的影响。结果表明:温度高于1 300℃时,复合烧结助剂熔融形成固溶体,从而实现SiC多孔陶瓷的低温烧结;随烧结助剂用量增加或烧结温度升高,SiC多孔陶瓷的开孔率和气体渗透速率均下降。在料浆中SiC陶瓷粉体体积分数为20%、烧结助剂质量分数为10%、醇水体积比为7:3、锂辉石与堇青石质量比为2:1的条件下,于1 370℃烧结后得到的SiC多孔陶瓷,孔隙率高、孔径分布集中(4~15μm),孔形貌呈均匀的三维无规则贯通结构,抗弯强度为8.5 MPa,开孔率达到67.9%,透气率为280.5 m~3/(m~2·Pa·h)。     

溶胶-凝胶法结合二步烧结制备陶瓷刚玉磨料的微结构控制及晶粒细化机理

以6μm粒径的拟薄水铝石为原料,采用溶胶-凝胶法制备含La₂O₃-TiO₂-SiO₂复合添加剂的陶瓷刚玉磨料的前驱体,然后分别采用传统烧结方法和二步烧结法制备陶瓷刚玉磨料。利用扫描电镜和透射电镜分析磨料的微观结构和元素分布,并采用imagePro软件对晶粒尺寸进行分析。结果表明,采用二步烧结法时,第一段烧结的温度显著影响磨料的最终晶粒尺寸。第二段烧结由于温度较低,烧结机制由晶界迁移变为晶界扩散,从而显著细化晶粒,并避免晶粒异常长大。适当降低第二段的烧结温度有利于获得分布均匀的细小等轴晶,但会导致磨料密度降低。与传统烧结法制备的刚玉磨料相比,二步烧结的磨料虽然密度降低,但晶粒细小、尺寸均匀,磨料仍具有较高的硬度。采用第一段和第二段烧结温度分别为1 300℃和1 200℃(保温10 h)的二步烧结法,可获得细小而均一的等轴晶,平均晶粒尺寸为(334±97) nm,密度和硬度(HV)分别为3.87 g/cm³和(18.3±0.29) GPa。     

利用铁尾矿制备SiC-Y3Al5O12复相陶瓷

以铁尾矿合成的SiC粉为原料,Y2O3和Al2O3为烧结助剂,常压烧结制备SiC-Y3Al5O12(YAG)复相陶瓷.通过X射线衍射及扫描电镜等测定材料的相组成和显微结构,并分析烧结物的致密化过程,研究其结构和力学性能.结果表明:制备材料适宜的烧结温度为1 800-1 850℃.烧成产物主要物相为SiC,其余为YAG和少量FexSiy随烧结温度的升高,Y2O3和Al2O3生成的YAG相逐渐增加且稳定存在.细小的YAG颗粒弥散在基体周围,并逐渐增多聚集把短柱状SiC晶粒粘结在一起起到促进烧结的作用.随烧结温度的升高,材料的显气孔率降低,而体积密度、硬度和抗压强度均增加.     

硅—钛—硼掺杂金刚石烧结过程的研究

采用x射线衍射分析和透射电镜观察,研究了硅-钛-硼掺杂金刚石在烧结过程中各物相的反应。随着烧结温度的升高,硅、钛分别与金刚石表面石墨化的碳反应生成SiC和TiC,硅与钛反应形成TiSi_2。在1500～1600℃,TiSi_2发生分解,新生的硅和钛与金刚石表面剩余的石墨反应生成相应的碳化物。通过金刚石颗粒间的碳化物的烧结,将金刚石粘结起来。     

高强度氧化钪陶瓷的制备技术研究

采用纯度4N以上(纯度99.99%)的Sc_2O_3为原料,分别通过真空烧结、热压烧结、热压预烧结和热等静压烧结相结合的方法制备了Sc_2O_3陶瓷。分别采用阿基米德法、扫描电镜(SEM)和万能试验机等对上述3种方法制备的Sc_2O_3陶瓷的密度、抗压强度和微观形貌进行分析。研究结果表明:通过真空烧结制备的Sc_2O_3陶瓷密度高达3.80 g·cm-3,抗压强度为460 MPa;利用热压烧结制备的Sc_2O_3陶瓷密度为3.72 g·cm-3,抗压强度为1100 MPa;通过热压预烧结和热等静压烧结相结合制备的Sc_2O_3陶瓷密度为3.84 g·cm-3,抗压强度高达1900MPa。在提高Sc_2O_3陶瓷密度的前提下,减小烧结体的晶粒可以显著提高其抗压强度。因此,采用热压预烧结和热等静压烧结相结合制备的Sc_2O_3陶瓷可以满足特殊使用的要求。     

自蔓燃高温合成碳化物陶瓷

介绍了自蔓延高温合成（SHS）制备碳化物粉体。单晶、多孔材料和致密材料。重点讨论了通过控制反应参数,控制合成材料的组织结构和性能的一些措施。以催化剂载体、泡沫陶瓷过滤器、粗TiC磨料以及Si-SiC复合材料为例,介绍了SHS在材料合成中的应用和控制方法。参考Ti3SiC2陶瓷的合成,讨论了多元SHS体系中产物相的控制问题。另外,文中还介绍了提高烧结助剂BxC在SiC中的分散性,从而提高SHSSiC烧结性的实例。     

溶胶-原位凝胶法制备金刚石/LZAS系陶瓷结合剂砂轮的结构与性能

以硝酸盐溶液、磷酸铵溶液、Si O2溶胶和金刚石颗粒制成混合料浆,经快速凝胶及干燥后,在850℃/1.5 h条件下烧结,得到金刚石/陶瓷结合剂复合体,通过对其微观结构以及表面粗糙度、抗弯强度和孔隙率等性能进行表征,研究混合料浆中的固相含量对金刚石/复合氧化物陶瓷复合体结构与性能的影响。结果表明:Si O2-Al2O3-Zn O-Na2O-Li2O-P2O5复合氧化物陶瓷结合剂的晶化程度高,晶型完整;随料浆中固含量增加,金刚石/陶瓷复合体的孔隙率先降低后升高,而抗弯强度则先升高后降低,当固含量(体积分数)为60%时,砂轮的孔隙率和抗弯强度分别达到最小值(26.2%)和最大值(69 MPa)。与传统粉末压制法制备的金刚石/复合陶瓷结合剂砂轮相比,采用溶胶-凝胶原位法制备的砂轮,结构均匀,抗弯强度和孔隙率分别提高约40.5%和34.8%,磨削加工的硬质合金工件表面无较深划痕,工件表面粗糙度为0.049μm。     

工程陶瓷的磨削钻孔及表面形成机理

结合工程陶瓷的加工特性,采用特定组份的铜基结合剂烧结金刚石钻头对其进行孔加工试验研究.结合剂体积分数为48%Cu、30%Co、6%Ni、5%WC、5%Ti、4%Sn、2%Cr.根据烧结金刚石钻头的磨削加工特点,导出了唇面单颗金刚石磨粒的平均载荷的计算公式;在此基础上,结合陶瓷磨削表面的扫描电镜观察,分析了金刚石钻头磨削钻孔的陶瓷材料去除机理.结果表明,在试验条件下,陶瓷材料虽然以脆性断裂去除为主,但也有部分材料发生塑性变形去除.     

Wear resistance of polycrystalline diamond cutters for drill bits

In the present work, the wear resistance of GES 1313 polycrystalline diamond (PCD) cutters (produced by E6), which are cylindrical in form (diameter 13.44 mm, height 13 mm), in turning granite and abrasive wheels at different speeds is investigated. The optimal cutting speed is determined, and comparative data are obtained for the cutting of Mansurovsk granite and 64C (SiC) abrasive wheels, so as to develop recommendations regarding the test conditions for PCD cutters. The wear resistance is characterized in two ways: as the ratio of the loss of volume of the diamond layer to the volume of machined material removed (when it is a dimensionless number); or by the quantity of machined material removed with a fixed degree of cutter wear (when it is expressed in cm³ with respect to 1-mm wear of the rear surface). In cutting granite, the cutting speed varies from 80 to 320 m/min; in cutting abrasive wheels, the cutting speed is 500 m/min. To calculate the volume of the PCD cutters, 3D models of the worn sections are constructed by means of Kompas 3D software, and a calibration curve for determining the volume of material removed by wear at the rear surface of the PCD cutters is plotted. The cutting angle is–22°. The change in volume of the worn section of the PCD cutter with change in the cutting angle from–20 to–25° is less than the measuring precision of the wear area up to 0.8-mm blunting. Increase in speed from 80 to 160 m/min in cutting granite reduces the wear resistance of the PCD cutters by a factor of 12. The relative wear of the PCD cutters in cutting granite is (0.01–0.02) × 10–6, which is 20 times less than in cutting 64C abrasive wheels. The relative wear of the PCD cutters in cutting abrasive wheels does not depend on the blunting of the rear surface up to values of 1.4 mm. This method may be recommended for rapid determination of the wear resistance of PCD. The proposed method of calculating the worn volume of the PCD by means of Kompas 3D or other appropriate software may be used to assess the relative wear resistance of abrasives and cutting materials.     

Correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation

This study is concerned with the correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation. The mixtures of TiC, SiC, Ti + SiC, or TiC+SiC powders and CaF₂ flux were deposited on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these mixtures. The surface composite layers of 1.2 to 2.1 mm in thickness were homogeneously formed without defects and contained a large amount (30 to 66 vol pct) of hard precipitates such as TiC and Ti₅Si₃ in the martensitic matrix. This microstructural modification, including the formation of hard precipitates in the surface composite layer, improved the hardness and abrasive wear resistance. Particularly in the surface composite fabricated with TiC + SiC powders, the abrasive wear resistance was greatly enhanced to a level 25 times higher than that of the Ti alloy substrate because of the precipitation of 66 vol pct of TiC and Ti₅Si₃ in the hardened martensitic matrix. During the sliding wear process, hard and coarse TiC and Ti₅Si₃ precipitates fell off from the matrix, and their wear debris worked as abrasive particles, thereby reducing the sliding wear resistance. On the other hand, needle-shaped Ti₅Si₃ particles, which did not play a significant role in enhancing abrasive wear resistance, lowered the friction coefficient and, accordingly, decelerated the sliding wear, because they played more of the role of solid lubricants than as abrasive particles after they fell off from the matrix. These findings indicated that high-energy electron-beam irradiation was useful for the development of Ti-based surface composites with improved abrasive and sliding wear resistance, although the abrasive and sliding-wear data should be interpreted by different wear mechanisms.     

Effect of structure of a magnetoabrasive material on its life in the polishing of metals

Conclusions The mechanism by which the particles of a magnetoabrasive powder disintegrate depends on their structure and determines the service performance of the material. The disintegra tion of the particles of the sintered Zh15KT material involves the plucking out of the abrasive component and its removal from the machining space. Under these conditions, the fall in the fraction of the abrasive component in the polishing powder and the resultant decrease of the mechanical wedging forces lower the pressure which the Zh15KT particles exert on the work surface and have an adverse effect on the operating performance of the powder as a whole. The particles of a cast material cease to be effective mainly through attrition. As their nonporous matrices possess high hardness and strength and contact be tween the magnetic matrices and the abrasive over their interfaces is continuous, the service life of a cast powder is much (more than twice) longer than that of the sintered Zh15KT powder agglomerates, in which, because of their high porosity, contact on the interfaces between the iron and titanium carbide particles is discontinuous.Translated from Poroshkovaya Metallurgiya, No. 3(231), pp. 98–101, March, 1982.     

Properties of VK6-diamond composites sintered in shock waves

Studies have been made on a composite of VK alloy with ASM 28/20 diamond powder sintered in shock waves, which has high compressive strength and a low diamond grain damage coefficient. The wear resistance in sliding friction in oil and with free abrasive is over 40 times that of VK6 hard alloy under the same conditions. The wear mechanism has been deduced from studies on the structure and composition of the layers formed at the frictional surface.Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, No. 4(364), pp. 102–105, April, 1993.     

一种高性能烧结摩擦材料摩擦剂的选择

研究了SiO_2,SiC,B_4C对金属基烧结摩擦材料物理机械性能,特别是摩擦磨损性能的影响。结果表明,同时添加SiO_2,SiC,B_4C作摩擦剂的材料比单独添加SiO_2或SiC,或同时添加SiO_2和SiC的材料综合性能优良。     

High stress abrasive wear mechanism of LM13-SiC composite under varying experimental conditions

An attempt has been made to understand the mechanism of material removal during two-body abrasive wear of Al-alloy (LM13)-SiC composite under varying experimental conditions through the wear surface and subsurface examination. It has been noted that the mechanisms of material removal during the wear process are primarily cutting and plowing, which lead to formation of continuous wear grooves. In the composite, SiC particles act as protrusions over the surface and protect the matrix from wear. But at higher applied load, coarser abrasive size, and larger sliding distances, some of the SiC particles get fractured into fine particles and scooped off from the wear surface leading to a higher wear rate. The subsurface studies show severe plastic deformation and finally formation of a mechanically mixed layer (MML) over the plastically deformed zone. The MML gets fractured during the wear process and finally removed by the formation of lateral and transverse cracking. The cracks are generally initiated at the interface of MML and the plastically deformed zone and propagate along the weaker region in MML. The material removal mechanism has been schematically presented in order to have a better understanding.     

Recent advances of high-pressure generation in a multianvil apparatus using sintered diamond anvils

The tried and tested multianvil apparatus has been widely used for high-pressure and hightemperature experimental studies in Earth science. As a result, many important results have been obtained for a better understanding of the components, structure and evolution of the Earth. Due to the strength limitation of materials, the attainable multianvil pressure is generally limited to about 30 GPa (corresponding to about 900 km of the depth in the Earth) when tungsten carbide cubes are adopted as second-stage anvils.Compared with tungsten carbide, the sintered diamond is a much harder material. The sintered diamond cubes were introduced as second-stage anvils in a 6-8 type multianvil apparatus in the 1980s, which largely enhanced the capacity of pressure generation in a large volume press. With the development of material synthesis and processing techniques, a large sintered diamond cube (14 mm) is now available. Recently,maximum attainable pressures reaching higher than 90 GPa (corresponding to about 2700 km of the depth in the Earth) have been generated at room temperature by adopting 14-mm sintered diamond anvils. Using this technique, a few researches have been carried out by the quenched method or combined with synchrotron radiation in situ observation. In this paper we review the properties of sintered diamond and the evolution of pressure generation using sintered diamond anvils. As-yet unsolved problems and perspectives for uses in Earth Science are also discussed     

An abrasive material based on silicon nitride for grinding unhardened steels

Conclusions A study was made of the strength of abrasive grains of silicon nitride and of the wear resistance of silicon nitride material under conditions simulating the operation of abrasive grains in a grinding wheel. It is shown that in grain strength the new silicon nitride material is superior to diamond, Kubonit, and El'bor and inferior to Geksanit-A, while in wear resistance in the microcutting of unhardened steel it is comparable with Geksanit-A. On the basis of an electron microscopical examination of the surface structure of a worn microtool a mechanism is proposed for the wear of a material based on silicon nitride in the grinding of unhardened steel. A material based on silicon nitride could be successfully used in abrasive tools for the rough grinding of unhardened ferrous alloys.Translated from Poroshkovaya Metallurgiya, No. 5(173), pp. 34–37, May, 1977.