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1.
Composites of Si3N4-SiC containing up to 30 wt% of dispersed SiC particles were fabricated via hot-pressing with an oxynitride glass. To determine
the effect of sintering time and SiC content on the mechanical properties and the cutting performance, the composites with
fixed 8 hr-sintering time and 20 wt% SiC content were fabricated and tested. Fracture toughness of the composites increased
with increasing sintering time, while the hardness increased as the SiC content increased up to 20 wt%. The hardness of the
composites was relatively independent of the grain size and the sintered density. For machining heat-treated AISI4140, the
insert with 20 wt% SiC sintered for 8 hr showed the longest tool life while the insert with 20 wt% SiC sintered for 12 hr
showed the longest tool life for machining gray cast iron. An effort was made to relate the mechanical properties, such as
hardness, fracture toughness and wear resistance coefficient with the tool life. However, no apparent relationship was found
between them. It may be stated that tool life is affected by not only the mechanical properties but also other properties
such as surface roughness, density, grian size and the number of the inherent defects in the inserts. 相似文献
2.
In this work, a bronze matrix (90 wt% Cu + 10 wt% Sn) was reinforced with SiC and graphite particulates using mechanical alloying and a subsequent current sintering technique. The mechanically ball-milled bronze hybrid matrix composite powders reinforced with 5.0 wt% SiC and 5.0 wt% graphite were cold-compacted on a 1040 steel substrate under a pressure of 300 MPa. The compacted structure was sintered at atmospheric conditions to nearly a full density within 10 min using current sintering, in which the powders were heated by a low voltage and high current and compressed simultaneously. The samples were sintered at three different applied currents (1,500, 1,700, and 1,900 A) to provide dense and well-bonded coatings on steel substrates. Microhardness testing and optical and scanning electron microscopes (SEM) were used for microstructural characterization of the hybrid composites. The tribological characterization of the resulting composites was tested by a block-on-disk method for determination of the wear loss and friction coefficient behaviors against a steel disk. It was pointed out that increasing applied current during the sintering/coating process resulted in obtaining high-hardness and wear-resistant hybrid composite coatings. 相似文献
3.
The conventional route for preparation of silicon carbide ceramics is by the use of pressureless sintering, hot pressing, or hot isostatic pressing of silicon carbide starting powders. High sintering temperatures (2073–2473 K) and the addition of sintering additives are normally used to enhance densification. These sintering additives, however, form second phases at grain boundaries which impair the mechanical properties of the material, particularly at high temperatures. It is therefore desirable that new processing routes are developed that overcome these difficulties. A proposed route is to use a polymeric pressure which can provide a Silicon carbide matrix as binding agent for silicon carbide powders, thus making the requirement for high temperatures and sintering additives unnecessary. This paper reports observations of the direct transformation of a polymeric precursor into amorphous Si–C, and crystalline SiC at low temperatures, and the use of this precursor as a binder for the production of SiC powder/ex-precursor SiC composites. 相似文献
4.
为了获得高密度、高性能、复杂结构的碳化硅陶瓷件,提出采用机械混合法制备含有黏结剂和乌洛托品固化剂的碳化硅复合粉体,对复合粉体进行激光选区烧结(SLS)形成陶瓷素坯,并对素坯进行气氛烧结和渗硅处理,使其与基体发生反应烧结,最终形成复杂陶瓷异形件。实验证明:若激光功率为8.0 W、扫描速率为2 000 mm/s、扫描间距为0.1 mm、单层厚度为0.15 mm,获得的 SLS 陶瓷样品密度和强度最好。对SLS试样进行合理的中温碳化和高温渗硅,所得碳化硅陶瓷烧结体的抗弯强度最高可达 81 MPa,相对密度大于86%。 相似文献
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6.
Fabrication of a Cam Using Metal Matrix Composites 总被引:1,自引:0,他引:1
R. Purohit R. Sagar 《The International Journal of Advanced Manufacturing Technology》2001,17(9):644-648
This work reports on studies on Al-SiC as a possible alternative material for a cam. Powder metal composite cams when mounted
on hollow shafts provide a high strength to weight ratio. The coefficient of thermal expansion is also low. A mixture of four
different compositions (10, 20, 25, 30 wt %) of SiC powder were prepared and mixed with A1 powders. Cams were fabricated using
cold isostatic compaction and subsequent sintering. A die was also fabricated to cast the cams. The various properties of
fabricated composite cams, namely, compressive strength, hardness, density, and surface roughness were measured, and their
variation with reinforcement content was studied. 相似文献
7.
Two different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si3N4) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro-structure. The first type of composite was prepared from as-received α-SiC and α-Si3N4 powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as-received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α-SiC transformed into β-SiC, and almost all the α-Si3N4 transformed into α-Si3N4 in the composites made from the as-received powders, while in the composites made from the deoxidized material the α-SiC remained untransformed and both α-Si3N4 and β-Si3N4 phases were present in significant quantities. High-resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ? 1 nm thick amorphous intergranular films in the composites prepared from as-received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β-SiC transformation taking place in the composites made from as-received powders by a liquid-phase sintering route. An incomplete liquid-phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material. 相似文献
8.
真空热压烧结SiC_p/Al复合材料的界面元素扩散及增强断裂机理 总被引:1,自引:0,他引:1
采用真空热压粉末冶金烧结工艺制备了含SiC颗粒体积分数分别为 5 %、15 %和 2 5 %的SiC颗粒增强铝基复合材料 ,结合其力学性能、扫描电镜和界面微区能谱分析结果 ,分析了SiC/Al复合材料的真空烧结过程中的界面现象 ,以及材料增强和断裂机理。结果表明 ,真空烧结过程中出现了界面反应 ,改善了界面结合强度 ,断裂破坏主要在基体上进行。随着SiC粒子体积分数的增加 ,SiCp/Al复合材料的抗拉强度增加 ,弹性模量显著增加 ,延伸率降低 ,材料脆性增加。 相似文献
9.
以硅渣和玻璃粉为原料,采用粉体直接烧结法制备多孔材料,研究了烧结温度(700~900℃)、烧结时间(15~120min)和升温速率(10~100℃·min^-1)对多孔材料表观密度、气孔率、物相组成、抗压强度的影响。结果表明:气孔结构均匀性随烧结温度的升高而降低;表观密度随烧结温度的升高先减小后增大,随保温时间的延长而增大,随升温速率的增大而减小,气孔率的变化趋势与表观密度的相反;多孔材料的主要物相为玻璃相和硅、SiC、SiO2、Ca2Al2SiO7等结晶相,且结晶度随烧结温度的升高而降低;抗压强度随烧结温度的升高呈先增大后减小的趋势;当烧结温度为750℃,升温速率为30℃·min^-1,烧结时间为30 min时,多孔材料的主晶相为硅和Ca2Al2SiO7,抗压强度最大(1.60MPa),表观密度为0.43g·cm^-3,气孔率为80%。 相似文献
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As one of the rapid prototyping technologies, ultraviolet-curable resin (UV-resin) curing was recently introduced into the manufacturing of resin bond abrasive tools. This research was conducted to evaluate the influence of nanosized alumina filler on the manufacturing of UV-resin bond diamond grinding wheel, and comparatively study the machining performance of filler-loaded and filler-unloaded tools. The UV-resin and diamond abrasive grains were prepared with nanosized alumina filler in a proportion of 0, 2.5, 5.0, 7.5, and 10 wt%. The cure depth, hardness, and tensile strength of the cured mixture was studied, and the interfacial bond between the diamond grain and cured resin matrix was investigated as well. Two UV-resin bond diamond grinding wheels were fabricated to examine the influence of filler loading on wear performance of the tools. Experimental results based on ceramic workpieces showed that the introduction of alumina filler improved not only the material properties of cured resin matrix but also led to a significant improvement on the abrasive machining performance of grinding wheel. 相似文献
12.
纳米氧化锆增韧氧化铝基陶瓷刀具材料的研究 总被引:4,自引:1,他引:3
利用纳米氧化锆的相变增韧和纳米颗粒的增韧作用,提高了氧化铝基体的综合力学性能。在氧化铝基体中添加不同含量的纳米3Y-ZrO2,纳米ZrO2含量为15wt%的A15Z材料综合力学性能达到最好(抗弯强度766.74MPa、断裂韧度6.13MPa·m1/2、维氏硬度18.32GPa),表明添加纳米氧化锆的复合刀具材料的力学性能远远超过单相氧化铝材料。 相似文献
13.
Densification of alumina components via indirect selective laser sintering combined with isostatic pressing 总被引:1,自引:0,他引:1
Kai Liu Yusheng Shi Wenting He Chenhui Li Qingsong Wei Jie Liu 《The International Journal of Advanced Manufacturing Technology》2013,67(9-12):2511-2519
To improve the final density of ceramic parts via indirect selective laser sintering (SLS), cold/hot isostatic pressing (CIP/HIP) technologies were introduced into the process. The proposed approach in the present study combined spray drying with mechanical mixing by which we prepared a kind of compound powder consisting of polyvinyl alcohol (PVA, 1.5 wt%), epoxy resin E06 (8 wt%), and alumina so as to get a good fluidity for SLS. At the first step, SLS parts reached the highest relative density of about 32 % when the laser energy density was 0.094 J/mm2, which facilitated the next operation and improvement of final density. Then, a soft polymer canning was prepared for CIP around the surface of SLS alumina ceramic parts using pre-vulcanized natural rubber latex RTV-2, gelation and film. Following that, we experimented on different CIP maximum pressure which had different effects on densification of SLS alumina parts, the whole process in CIP was divided into three stages of I, II, and III. Based on thermal gravity curve of epoxy resin E06, ignoring the impacts of the only 1.5 wt% PVA on degreasing, green bodies were degreased and furnace-sintered. Finally, the relative density of alumina parts reached 95.94 % after HIP process. Field emission scanning electron microscopy was used to analyze the densification evolvement in each stage of process and the fracture mechanism. The study showed a positive and practical approach to manufacture ceramic matrix and ceramic components with complex shape by indirect SLS technology. 相似文献
14.
通过宏观实验发现在切削过程中刀具的Al2O3/SiC界面发生了断裂;建立了碳化硅增韧氧化铝基陶瓷刀具切削Inconel718镍基合金的分子动力学模型和单一界面的Al2O3/SiC三维界面模型,从原子尺度分析碳化硅增韧氧化铝切削过程的界面行为。在原有势函数的基础上计算了刀具与工件原子间、刀具内部基体与增韧间的Morse势函数,分别计算了单相Al2O3、单相SiC、复相Al2O3/SiC单一界面的界面结合能。研究结果表明:与单相界面相比,复相Al2O3/SiC界面结合强度较高,SiC增韧能够增强刀具的韧性和强度,但切削过程中出现了工件原子扩散到刀具中的现象。对扩散后刀具基体和增韧间形成界面的界面结合能进行了计算,发现刀具的界面结合强度有所降低,使刀具在Al2O3/SiC界面处发生断裂。 相似文献
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16.
为了解决FeS/Cu粉末冶金复合材料中FeS易团聚以及界面结合差的问题,采用机械合金化技术制备了FeS/Cu复合材料粉末。利用扫描电镜、X射线衍射仪、金相显微镜等对不同球磨时间的质量分数为6%的FeS/Cu合金粉末的混合特性、压制特性及烧结后的力学性能进行检测和分析,结果表明:机械合金化可有效改善FeS颗粒与基体合金粉末的混合均匀性,烧结后材料的密度、硬度均得到提高,FeS和Cu界面结合良好;由于FeS颗粒均匀弥散地分布在铜合金基体中,割裂了基体材料的连续性,反而使复合材料的韧性和压溃强度有所降低。 相似文献
17.
Matrix/reinforcement interface has a critical role in determining the properties of metal matrix composites (MMCs). Properties of matrix/reinforcement interface depend on the fabrication method. The main problem in the fabrication of MMCs is wettability between reinforcing particles and molten alloy. Al206/5 vol% aluminap cast composites were fabricated by the addition of reinforcing particles into molten Al alloy, semi-solid and liquid states, in two different forms: (1) as-received alumina (nano/micro) particles and (2) pre-synthesized composite reinforcement prepared via ball milling of alumina (nano/micro) with Al and Mg powders (master metal matrix composite). The effects of powder addition techniques, alumina/matrix interfacial bonding strength, and morphological characteristics of alumina particles on wear behavior were investigated. A new combination parameter, called alumina particle appearance (APA) index, was introduced. APA index approximates the collective effects of morphological characteristics of alumina particles on wear behavior. It is suggested that samples with lower APA index have superior wear properties. Microscopic examinations of the composite and matrix alloy and alumina/matrix interface were studied by scanning electron microscopy and transmission electron microscopy. It was found that wear resistance was increased in the composites fabricated by the addition of pre-synthesized reinforcing particles into molten alloy in the semi-solid state. Improvement in wear resistance is attributed to higher bonding strength of matrix/reinforcement as well lower APA index compared to those prepared via as-received alumina particles. 相似文献
18.
在316L不锈钢粉中分别添加10%的TiC、WC、NbC、Al2O3、Si3N4五种增强体,研究了各种增强体与不锈钢基体的反应性及对烧结过程的影响。结果表明:TiC、WC、NbC与不锈钢基体有良好的相容性,能均匀分布到不锈钢基体中,可以有效提高其强度,添加TiC的不锈钢还表现出优越的耐腐蚀性;由于Al2O3与基体不锈钢相容性过差,不能发挥增强体的作用,使材料的强度和耐蚀性不良;添加Si3N4的不锈钢在烧结过程中Si3N4发生分解,弥散强化了基体,硅有促进烧结的作用,而氮均匀渗透到不锈钢中,有利于形成高强度的高氮钢,从而使其相对密度、硬度及耐蚀性都高于其他材料。 相似文献
19.
不同晶型纳米氧化锆增韧氧化铝基陶瓷刀具材料研究 总被引:2,自引:0,他引:2
利用不同晶型纳米氧化锆的相变增韧和纳米颗粒的增韧作用来提高氧化铝基体的综合力学性能。研制成功了纳米ZrO2增韧氧化铝基陶瓷刀具材料A15Zc和A20Z(c+m),在其最佳烧结工艺条件下,A15Zc和A20Z(c+m)材料的抗弯强度、断裂韧度和维氏硬度分别为812.83MPa、5.5MPa.m1/2、16.68GPa和869.48MPa、5.85MPa.m1/2、16.09GPa。刀具的主要增韧机理是相变增韧、裂纹偏转、裂纹弯曲和纳米颗粒的桥连等。 相似文献