耐磨铸件铸渗陶瓷技术的初探

金属基陶瓷复合材料制作的立磨磨辊和磨盘、锤头、板锤、立轴破叶轮等耐磨铸件,都有较成熟的应用,也显示出非常优越的性价比。进口的陶瓷/高铬铸铁复合材料与高铬铸铁两种材质在立磨上应用,有的效果好,有的也存在表面陶瓷块剥落的现象。某公司近年来开展了在耐磨铸件上铸渗陶瓷的研发试验,涉及陶瓷颗粒、陶瓷棒和陶瓷块;其金属基体材料有高锰钢、高铬铸铁、灰铸铁、球铁和碳钢等。从大量的文献报导来看,我国铸渗陶瓷技术的研究方兴未艾,但是在耐磨铸件上的工业性应用尚处于初期阶段。     

纤维增强铝硅酸盐玻璃陶瓷磨损失效机理研究

在UMT-2微观磨损试验机（USA）上研究了SiC纤维在复合材料摩擦行为过程中的作用,讨论了纤维含量、摩擦行为过程对复合材料摩擦学性能的影响,并对纤维增强铝硅酸盐玻璃陶瓷复合材料的磨损失效机理进行了探讨。研究结果表明：SiC纤维/玻璃陶瓷复合材料摩擦系数随对磨时间的变化是由起始时的较低值逐步过渡到稳态数值,但在摩擦过程的后期摩擦系数表现出明显的波动。复合材料的磨损失重随磨损时间的延长而逐渐增大,复合材料的耐磨性能下降,磨损失重增加。复合材料基体与摩擦对磨件间存在粘着现象,但其主要磨损失效形式仍为磨粒磨损和疲劳磨损。复合材料界面结合性能与磨损表面上纤维的排列对复合材料的摩擦学性能是有较大影响的。     

PTFE/纳米SiC复合材料的摩擦磨损性能研究

利用冷压烧结法制备了不同含量的聚四氟乙烯/纳米碳化硅(PTFE/纳米SiC)复合材料。采用MM-200型摩擦磨损试验机在干摩擦条件下考察了纳米SiC含量及载荷对PTFE/纳米SiC复合材料摩擦磨损性能的影响,借助于扫描电子显微镜观察分析了试样磨损表面形貌,并探讨了其磨损机理。结果表明,纳米SiC能够提高PTFE/纳米SiC复合材料的硬度和耐磨性,当纳米SiC质量分数为7%时,PTFE/纳米SiC复合材料的磨损量最小,摩擦系数也最小;随纳米SiC含量的增加,其摩擦系数有所增大;随着载荷的增大,PTFE/纳米SiC复合材料的磨损量增加。     

硅纳米材料与玻璃纤维混杂填充PA6复合材料的摩擦磨损性能研究

采用MM-200型摩擦磨损试验机对在干摩擦条件下3种硅纳米材料（纳米SiC、SiO2及Si3N4）与玻璃纤维混杂填充聚酰胺6（PA6）复合材料与45#钢对磨时的摩擦磨损性能进行了研究,并采用扫描电子显微镜对复合材料的磨损表面进行了观察。结果表明,3种纳米硅材料都能减小复合材料的摩擦因数,其中以纳米SiO2与玻璃纤维混杂效果最佳,纳米SiC、SiO2及Si3N4的最佳含量分别为3 %、5 %和3 %。纳米SiO2和纳米Si3N4能够提高复合材料的耐磨性,而纳米SiC会导致复合材料的磨损量增大。     

偶联修饰纳米碳化硅/聚四氟乙烯基复合材料的摩擦磨损性能

通过冷压烧结法制备了聚四氟乙烯(PTFE)与钛酸酯和硅烷偶联剂修饰的纳米碳化硅(nano-SiC)复合材料,采用45#钢为摩擦对偶件的MM-200型摩擦磨损试验机,在室温干摩擦条件下测试了复合材料的摩擦学性能,用扫描电子显微镜(SEM)对磨损表面进行了观察并分析了磨损机理。结果表明:纳米SiC的加入能提高PTFE复合材料的硬度和耐磨性;偶联修饰改善了复合材料的摩擦学性能;与硅烷相比,钛酸酯偶联修饰nano-SiC/PTFE复合材料的硬度和摩擦学性能更好。两种偶联修饰复合材料的表面磨损情况相似,主要表现为粘着磨损,而未经偶联处理nano-SiC的复合材料在粘着磨损的同时出现了疲劳磨损。     

纳米SiC或Si3N4与玻璃纤维混杂填充PA6复合材料摩擦磨损性能研究

采用注塑成型法制备纳米SiC或Si3N4与玻璃纤维混杂填充PA6尼龙复合材料。采用MM-200型摩擦磨损试验机在干摩擦条件下考察了纳米颗粒含量及载荷对PA6复合材料摩擦磨损性能的影响。采用扫描电子显微镜观察分析磨损表面形貌及磨损机理。结果表明:纳米Si3N4与玻璃纤维混杂能使复合材料耐磨损性提高,以3%Si3N4与玻璃纤维混杂填充耐磨性最佳;而纳米SiC与玻璃纤维混杂会导致复合材料的磨损量增大,纳米SiC或Si3N4与玻璃纤维混杂填充PA6复合材料的摩擦系数都低于尼龙材料。     

Sialon及SiC陶瓷对金属摩擦副磨损性能的研究

为了使结构陶瓷能够在汽车发动机的某些摩擦副中得到应用,对Sialon(Si_3N_4基陶瓷)及SiC结构陶瓷对钢的摩擦副的摩擦磨损性能进行了研究。还作了钢对钢及冷激铸铁对钢的摩擦磨损性能的对比试验。结果表明:Sialon及SiC陶瓷对钢的摩擦系数比钢对钢及冷激铸铁对钢的摩擦系数小。在抗磨损性能方面,Sialon及SiC陶瓷试块即使在试验载荷比钢及冷激铸铁试块大的情况下,不但陶瓷试块的磨损量比金属试块的磨损量要小得多,而且与陶瓷试块相匹配的钢环的磨损量也比与金属试块相匹配的钢环的磨损量要小。用上述结构陶瓷材料制成汽车发动机中的某些零件以代替金属零件,不仅陶瓷零件本身耐磨性好,而且与陶瓷零件匹配的金属零件的磨损也会减小。     

陶瓷防护树脂基复合材料的磨损性能及机理研究

为了提高树脂基复合材料的耐磨损性能,采用Al2O3陶瓷贴片制备了陶瓷防护复合材料,通过往复式摩擦磨损试验机对陶瓷片材和复合材料进行了磨损性能试验,得到了防护复合材料在不同加载参数下的磨损形貌,进一步采用三维白光干涉表面形貌仪测试了磨损试样的表面形貌、磨痕深度与宽度,并据此建立了磨损性能数据分析与评价模型,分析了防护复合材料的耐磨损机理。结果表明:复合材料采用陶瓷贴片进行防护可大大提高其耐磨损性能,经陶瓷防护后,复合材料的可承受加载载荷从40 N提高至100 N;随着载荷的进一步增加,陶瓷防护复合材料的磨痕深度大大增加,而钢球的磨损程度迅速下降,其磨损机制发生了变化。分析了造成复合材料磨损性能发生变化的原因。     

纤维增强铝硅酸盐玻璃陶瓷复合材料的摩擦学特性研究

在UMT-2微观磨损试验机（USA）上研究了SiC纤维增强铝硅酸盐玻璃陶瓷复合材料的摩擦学特性,且对摩擦表面进行了SEM观察和分析。研究结果表明：随着SiC纤维含量的增加,摩擦系数逐渐降低,但变化幅度较小。而当纤维含量（体积）低于25％时,复合材料的磨损量明显降低,而显微硬度却有较大提高;超过25％时,继续增加纤维的含量会导致复合材料耐磨性下降。SiC纤维增强铝硅酸盐玻璃陶瓷复合材料的摩擦系数随着载荷的增大显现先增大后减小的趋势,并且在载荷140N时达到最大值,而磨损量随着载荷的增大而增加。复合材料的主要磨损失效形式为磨粒磨损。     

纳米SiC及其与石墨、二硫化钼填充PTFE基复合材料摩擦磨损性能研究

用摩擦磨损试验机对纳米碳化硅（SiC）及其与石墨、二硫化钼（MoS2）混合填充聚四氟乙烯（PTFE）复合材料在干摩擦条件下与45#钢对磨时摩擦磨损性能进行了研究,用洛氏硬度计对PTFE及其复合材料的硬度进行了测量,用扫描电子显微镜对PTFE复合材料磨损表面进行了观察。结果表明,纳米SiC的加入能提高PTFE复合材料的硬度和耐磨性,纳米SiC与MoS2混合填充会使PTFE复合材料的耐磨性提高更多,特别是在载荷增大时其耐磨效果更好。纳米SiC填充PTFE复合材料的摩擦因数比纯PTFE大,且随载荷增加有所减小, MoS2、石墨的加入可降低PTFE的摩擦因数。     

Tribological Behavior of SiC-Whisker/Al2O3 Composites against Carburized 8620 Steel in Lubricated Sliding

Mineral oil lubricated sliding tests of Sic-whisker (SiC_w,)/A1₂0₃ composites and monolithic alumina against carburized 8620 steel were conducted on a cylinder-on-cylinder machine. The wear rate of the composites was one or two orders of magnitude less than that of pure alumina. Hot-pressed 25 wt% SiC_w,/A1₂0₃ composite had a lower wear rate than sintered and HIPed 7.5 wt% SiC/Al₂O₃ composite under the same conditions. The weight loss of the steel mating ring against the 25 wt% SiC_w, composite was a factor of four lower than against the 7.5 wt% SiC_w, composite, but the former was a factor of 50 to 60 less than that against pure alumina. The composites showed lower friction coefficients than alumina during the run-in stage. The friction coefficients decreased with initial wear. The steady-state friction coefficient decreased with increasing load up to 500 N for hot-pressed 25 wt% SiC,/Al₂0₃ composite. Further, SEM observation showed much less microfracture in composites than in alumina. EDAX analysis revealed less Fe transfer from the steel ring to the composites than to pure alumina. Wear by microfracture and by adhesion in composites was suggested to be suppressed by SIC whiskers. This in turn reduced wear of the steel because of the generation of fewer hard particles.     

载荷对纳米SiC/BMI-BA复合材料摩擦性能的影响

利用高速机械剪切的方法将纳米SiC粒子分散在双马来酰亚胺树脂预聚体（BMI-BA）中，以浇铸成型法制备了纳米SiC／BMI—BA复合材料，在M-200型磨损机上研究了不同载荷下纳米SiC的填充量对复合材料摩擦系数和磨损率的影响，利用扫描电镜（SEM）观察了纳米SiC质量分数为6．0％时复合材料及其对摩环在不同载荷下的表面形貌。结果表明：纳米SiC能够显著降低复合材料的摩擦系数及磨损率，尤其是在高载荷下这种作用更明显。SEM显示BMI树脂发生的是塑性变形和疲劳磨损，而复合材料主要是粘着磨损。     

The tribological properties of SiC whisker-reinforced polyetheretherketone

SiC whisker-reinforced polyetheretherketone (PEEK) composites with different filler proportions were made into block specimens by compression molding. The friction and wear properties of the composites were investigated on a block-on-ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block under ambient conditions. The morphologies of the wear traces and wear debris were observed by scanning electron microscopy (SEM). It was found that SiC whisker-reinforced PEEK exhibited considerably lower friction coefficient compared with pure PEEK, while SiC whisker as a filler at a content of 1.25 to 2.5 wt % was very effective in reducing the wear rate of PEEK. Especially, the lowest wear rate was obtained with the composite containing 1.25 wt % SiC whisker. The SEM pictures of the wear traces indicated that PEEK composites undertook abrasive wear that was enhanced with increasing SiC whisker content, while for the frictional couple of carbon steel ring/composite block (reinforced with 1.25 wt % filler), a thin, uniform, and tenacious transfer film was formed on the ring surface. It was also supposed that the differences in the content of SiC whisker as filler could cause the differences in the wear mechanisms of SiC whisker-reinforced PEEK composites. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2341–2347, 1998     

Compressive strength and wear properties of SiC/Al6061 composites reinforced with high contents of SiC fabricated by pressure-assisted infiltration

Pressure-assisted infiltration was used to synthesize SiC/Al 6061 composites containing high weight percentages of SiC. A combination of PEG and glass water was used to fabricate SiC preforms and the effect of the presence of glass water on the microstructure and mechanical properties of the preforms was evaluated by performing compression tests on the preforms. Also, the compressive strength and the hardness of the SiC/Al composites were investigated. The results revealed that the glass water improved the compressive strength of the preforms by about five times. The microstructural characterization of the composites showed that the penetration of the aluminum melt into the preforms was completed and almost no porosity could be seen in the microstructures of the composites. Moreover, the composite containing 75 wt% SiC exhibited the highest compressive strength as well as the maximum hardness. The results of the wear tests showed that increasing the SiC content reduces the wear rate so that the Al-75 wt% SiC composite has a lower wear rate and a lower coefficient of friction than those of Al-67 wt% SiC composite. This indicated higher wear resistance in these composites than the Al alloy due to the formation of a tribological layer on the surface of the composites.     

In situ synthesis of TiC–TiB2–hBN–SiC composites through SHS

Ceramic composite powders with novel composition were synthesized in situ by the combination of two different reactions in one step.

The high exothermicity of a reaction previously investigated for the synthesis of TiC–TiB₂ powders was exploited to carry a second low exothermic reaction for the production of hBN–SiC composites in a self-propagation regime. The overall reaction exhibited sufficient exothermicity to self-sustain till completion.

The process yielded high purity powders with tailored compositions suitable for the fabrication of ceramic and cermet materials characterized by wear resistance and self-lubricant behaviour shown by the presence of hBN intimately dispersed into the hard ceramic matrix.     

Influence of Microstructure on the Wear Behavior of SiC-Reinforced Titanium-Matrix Composites Lubricated by Water and by Ethanol

Two kinds of SiC-reinforced titanium-matrix composites were slid against themselves in water and in ethanol to evaluate the influence of their microstructure on the wear behavior. The composites had a structure in which the SiC particles were coated with interfacial layers that consisted of Ti₅Si₃C _x and TiC, and the TiC particles were dispersed in a titanium matrix. The wear resistance of the composites was much better than that of titanium metal. The wear of the composites prepared from starting materials with a high SiC content was lower than that with a low SiC content.     

碳/碳化硅摩阻复合材料的研究进展

碳/碳化硅是近年来发展起来的一种新型高性能陶瓷基摩阻材料,具有密度低,抗氧化性好,摩擦性能高且性能稳定等一系列优点,在高速列车、飞机和重型汽车等高能载制动领域具有广泛的应用前景.反应性熔体浸渗法是制备碳/碳化硅摩阻复合材料的有效途径.从碳/碳化硅摩阻复合材料的设计出发,深入分析了反应性熔体渗透过程的热力学条件,Si-C反应体系的基本特征以及动力学规律.针对短纤维模压和三维针刺等两种典型C/SiC复合材料的制备过程,对材料的微结构特征和摩擦磨损性能进行了系统论述.同时,对红外热成像、X射线透射和工业CT等先进工程检测方法在碳/碳化硅摩阻复合材料构件上的应用进行了分析.     

Fine diameter ceramic fibres

Two families of small diameter ceramic fibres exist. The oxide fibres, based on alumina and silica, which were initially produced as refractory insulation have also found use as reinforcements for light metal alloys. The production of SiC based fibres made possible the development of ceramic matrix composites. Improved understanding of the mechanisms which control the high temperature behaviour of these latter fibres has led to their evolution towards a near stoichiometric composition which results in strength retention at higher temperatures and lower creep rates. The SiC fibres will however be ultimately limited by oxidation so that there is an increasing interest in complex two phase oxide fibres composed of α-alumina and mullite as candidates for the reinforcement of ceramic matrices for use at very high temperatures. These fibres show low creep rates, comparable to the SiC based fibres but are revealed to be sensitive to alkaline contamination.     

Friction and wear characteristics of ceramic particle filled polytetrafluoroethylene composites under oil-lubricated conditions

Five kinds of polytetrafluoroethylene (PTFE)-based composites were prepared: PTFE, PTFE + 30 vol % SiC, PTFE + 30 vol % Si₃N₄, PTFE + 30 vol % BN, and PTFE + 30 vol % B₂O₃. The friction and wear properties of these ceramic particle filled PTFE composites sliding against GCr15 bearing steel under both dry and liquid paraffin lubricated conditions were studied by using an MHK-500 ring-block wear tester. The worn surfaces and the transfer films formed on the surface of the GCr15 bearing steel of these PTFE composites were investigated by using a scanning electron microscope (SEM)and an optical microscope, respectively. The experimental results show that the ceramic particles of SiC, Si₃N₄, BN, and B₂O₃ can greatly reduce the wear of the PTFE composites; the wear-reducing action of Si₃N₄ is the most effective, that of SiC is the next most effective, then the BN, and that of B₂O₃ is the worst. We found that B₂O₃ reduces the friction coefficient of the PTFE composite but SiC, Si₃N₄, and BN increase the friction coefficients of the PTFE composites. However, the friction and wear properties of the ceramic particle filled PTFE composites can be greatly improved by lubrication with liquid paraffin, and the friction coefficients of the PTFE composites can be decreased by 1 order of magnitude. Under lubrication of liquid paraffin the friction coefficients of these ceramic particle filled PTFE composites decrease with an increase of load, but the wear of the PTFE composites increases with a load increase. The variations of the friction coefficients with load for these ceramic particle filled PTFE composites under lubrication of liquid paraffin can be properly described by the relationship between the friction coefficient (μ) and the simplified Sommerfeld variable N/P as given here. The investigations of the frictional surfaces show that the ceramic particles SiC, Si₃N₄, BN, and B₂O₃ enhance the adhesion of the transfer films of the PTFE composites to the surface of GCr15 bearing steel, so they greatly reduce the wear of the PTFE composites. However, the transfer of the PTFE composites onto the surface of the GCr15 bearing steel can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. Meanwhile, the interactions between the liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, create some cracks on the worn surfaces of the ceramic particle filled PTFE composites; the creation and development of these cracks reduces the load-supporting capacity of the PTFE composites. This leads to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2611–2619, 1999