纳米晶粒精密电铸层力学性能的试验研究

采用高频窄脉宽脉冲电流、高速冲液等方法获得金属镍纳米晶粒精密电铸层。分析、研究了晶粒大小对沉积层力学性能的影响。结果表明,随着晶粒尺寸的减小,沉积层微观硬度和强度性能得到了明显提高。常温条件下,沉积层晶粒从1 000nm细化至70nm时,其抗拉强度可提高至1 160MPa,但随着沉积层晶粒进一步细化,其抗拉强度呈下降趋势,出现与传统的Hall-Patch理论相背离现象。200℃时,得到和常温条件下类似结果,而400℃时,其抗拉强度随着晶粒的细化基本保持不变     

纳米晶精密电铸层微观结构的测试与研究

采用高速冲液电铸装置、高频脉冲电流等方法，制备出金属镍纳米晶粒电铸沉积层。运用TEM、SEM和XRD等现代分析手段对纳米晶沉积层微观结构进行了分析研究。结果表明，沉积电流密度对细化沉积层晶粒有着重要影响。随着沉积层晶粒细化，横断面上晶粒生长从树枝状晶向细小等轴～柱状晶方式转变，在(200)晶面存在着明显择优生长取向。分析了细化晶粒对沉积层内应力的影响。     

纳米复合材料的微细电铸技术研究

为提高电铸微器件的力学性能,研究了镍-纳米氧化铈颗粒复合电铸工艺,分析了电铸参数(电流密度、纳米氧化铈颗粒浓度及转速)对沉积层中纳米氧化铈颗粒含量、沉积层微观结构及织构、沉积层微观硬度的影响.试验结果表明,电流密度对沉积层中纳米氧化铈颗粒含量具有重大影响.由于纳米氧化铈颗粒的加入,使得沉积产物的晶粒细化,择优取向由(220)逐步转变为(111),微观硬度显著增强.     

基于纳米氧化镧的精密电铸工艺试验研究

采用纳米稀土La2O3为添加剂，研究其对电铸镍溶液特性、铸层微观结构及其性能的影响。通过对沉积过程中阴极极化曲线的测定，探讨了纳米La2O3在电极表面的作用机理，并采用SEM、XRD等现代分析手段对电铸层微观结构进行了测试和分析。试验结果表明：纳米La2O3能够在阴极表面发生特性吸附，增大阴极极化，细化精密电铸层晶粒，提高铸层的均匀性；晶粒生长在（220）晶面方向上存在明显的择优取向；获得的电铸层显微硬度比普通电铸层有显著提高。     

基于稀土LaCl3的精密电铸工艺研究

以稀土LaCl3作为添加剂，通过极化曲线、微分电容测定，探讨了稀土LaCl3对电铸镍铸液性能的影响及其在电极表面的作用机理，并采用SEM、XRD等现代分析手段对镍电铸层微观结构进行测试。试验结果表明：LaCl3能够在阴极表面发生特性吸附，增大阴极极化，细化精密电铸层晶粒，提高精密电铸的沉积速度，电铸层的显微硬度得到显著提高。     

纳米晶脉冲电铸的试验研究

通过理论分析和试验研究 ,利用高频脉冲电流、高速冲液及添加剂方法 ,获得了纳米晶电铸层。分析了在脉冲电铸过程中 ,电规准及添加剂对沉积层微观结构影响     

镍-氧化镧纳米颗粒复合电铸的研究

采用复合电铸工艺制取了含La2 O3 纳米颗粒的镍基复合电铸层 ,研究了La2 O3 纳米颗粒共沉积量对复合电铸层微观组织及显微硬度的影响。结果表明 ,随着La2 O3 纳米颗粒共沉积量的增大 ,复合电铸层表面更加平整、组织也更加细致均匀 ,基质金属镍的晶粒得到进一步细化 ,因而复合电铸层的显微硬度也随之升高。     

添加稀土元素对精密电铸层组织与性能的影响

将稀土LaCl3作为添加剂，进行精密电铸试验，研究了稀土阳离子对铸液特性、铸层微观结构及其性能的影响，分析了稀土阳离子在阴极沉积表面的作用机理。结果表明：稀土阳离子在沉积表面能产生特性吸附，具有增强阴极极化、提高沉积过电位和细化铸层晶粒的作用；沉积过程中晶粒在（111）晶面方向上存在明显的择尤生长取向；铸层的显微硬度得到显著提高。     

镍锰合金的纳米晶电铸

电铸镍锰合金因其特殊的性能而具有重要的应用前景。分析了电沉积纳米晶材料的原理 ,在此基础上采用高速冲液、直流和高频脉冲电流以及电解液中加入添加剂等方法进行了镍锰合金的电铸试验 ,并对电铸层的锰含量、表面形貌和晶粒尺寸进行了测试。试验结果实现了镍锰合金的纳米晶电铸。讨论了锰含量、电流密度和添加剂等因素对电铸层晶粒尺寸和表面形貌的影响。     

添加纳米氧化镧的脉冲电铸试验研究

采用超窄脉宽脉冲电流、扫描电子显微镜和X射线衍射仪等现代分析手段和工具，以纳米稀土La2O3为电铸液添加剂，研究了脉冲电参数对电铸层微观结构及力学性能的影响。试验结果表明：由于纳米稀土La2O3的独特吸附作用，脉冲条件下获得的电铸层晶粒细小，组织均匀，其力学性能明显优于普通直流电铸层的力学性能；在ton为100μs、toff为500μs、电流密度为3A／dm^2时，铸层显微硬度和耐磨性比普通电铸层有显著提高。     

A study on cubic boron nitride (CBN) milling of hardened cast iron for productive and quality manufacturing of machine tool structural components

To improve efficiency and cost performance of cast iron machine tool component fabrication, an alternative process must be developed in order to replace the grinding process, which often causes a bottleneck in production. As an alternative manufacturing approach, this research applies cubic boron nitride (CBN) hard milling operations to eliminate the grinding process in order to improve the overall manufacturing process. A variety of hardened cast iron materials with Al and Mg additives and CBN tool types were prepared and tested based on a design of experimentation (DOE) to observe their effect on surface quality and tool life. Al and Mg were added to raw cast iron to achieve generation of oxide layers at the cutting edge during milling to protect the tool from wear. By executing the DOE, the optimal cutting conditions for achieving the best surface quality were introduced. Also, additional machinability tests were conducted with the optimal conditions in order to evaluate tool wear characteristics and surface quality of the machined workpieces. Based on the observation of the used tool by electron probe micro-analyzer (EPMA), a protective oxide layer of additives was observed at the cutting edge. Hardened cast iron with Al and Mg additives is found to show preferable wear and surface quality characteristics.     

Effects of Using Alternative Extreme Pressure (EP) and Anti-Wear (AW) Additives with Oxy-Nitrided Samples

Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphate-containing lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces.     

Strength measurement and textural characteristics of tropical residual soil stabilised with liquid polymer

The stabilisation of soils with additives is a chemical process that can be used to improve soils that contain weak engineering properties. The effects of non-traditional additives on the geotechnical properties of soils have been the focus of much investigation in recent years. It has been well established that the plasticity index and also the size, shape, and arrangement of soil particles will affect the treatment process of natural soils with additives. In this study, a commercial liquid polymer (SS299) was used to improve the strength of Malaysian residual soil. Unconfined compressive strength (UCS), field emission scanning electron microscopy (FESEM), N₂-BET surface area, and particle size analysis tests were used to investigate the influence of SS299 and the plasticity index on the time-dependent compressive strength and textural characteristics of tropical residual soil. The UCS results showed that the addition of 6% (as the optimum amount) of the selected additive increased the compressive strength of laterite soil noticeably, after 7 days of curing period. In addition, the increased compressive strength of the treated samples with the curing time was evident. Based on the FESEM results, it was found that the stabilisation process modified the porous network of the laterite soil. Furthermore, new white layers of reaction products were formed on the surface of clay particles.     

XPS and XANES characteristics of tribofilms and thermal films generated by two P- and/or S-containing additives in water-based lubricant

Two phosphates were synthesized and their tribological properties as water-soluble lubricant additives were evaluated by using four-ball tester. The micro/nano-scale chemical characteristics of tribofilms and thermal films formed from these additives in different conditions were explored by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) spectroscopy. The results show that the additives have better anti-wear and friction reducing properties than the oleate solution at higher load. Surface analysis results indicate that tribofilms are mainly composed of absorbed layer and chemical reactant layer, in which phosphorus exists in the form of adsorbed molecule, phosphate or polyphosphate, and sulfur in the form of alkyldisulfide, sulfide and sulfate. As to the thermal films, phosphate (or polyphosphate) and sulfate are detected as the main components. The anti-wear and friction-reducing performances can be ascribed to the formation of films on the metal surface, and the mechanism of the process of molecules adsorption, new compounds production through tribochemical reactions, film formation and destruction.     

氮碳共渗-渗硫复合层的摩擦学行为

采用离子氮碳共渗-离子渗硫复合处理技术在CrMoCu合金铸铁表面制备了氮碳共渗-渗硫复合层,并对未渗及复合渗表面在含硫添加剂液体石蜡润滑下的摩擦学行为及其磨损表面形貌和成分进行了测试.结果表明,在含硫添加剂润滑下,复合层与含硫添加剂产生协同作用,生成钼的化合物、磷酸盐和硫化物等化学反应膜使复合渗表面的摩擦系数较未渗表面降低了25%,耐磨性较未渗表面提高了50.1%.     

Effect of lubricating oil additives on particle size distribution and total number concentration in diesel engine

This paper investigates the characteristics of particle size distribution in exhaust gas of engine fuelled with pure diesel and with diesel mixed with base oil or with oil additives. The experiments are conducted on a turbocharged diesel engine with fast particulate spectrometer DMS 500 connected to the exhaust pipe. Base oil and two kinds of commonly used lubricating oil additives, antioxidant additives and antifoaming additives, are chosen to be added into the fuel, with the concentrations being 0.5%, 1.0% and 1.5% of fuel weight individually. The particle size distribution is measured under medium load (100 Nm) and full load at different speeds. The results indicate that the existence of base oil or oil additives shows great influence on particle size distribution. Copyright © 2012 John Wiley & Sons, Ltd.     

The application of Auger electron spectroscopy to the study of wear surfaces

An integrated approach employing semiquantitative Auger electron spectroscopy (AES) depth profile analysis and mechanical wear in a Reichert cylinder-on-disc machine was applied to the study of worn surfaces under heavy load conditions in the presence of extreme pressure (EP) additives. A significant correlation between the sulphur content of the topmost reaction layer and the wear behaviour was observed, although the worn surfaces were not ideal for AES analysis. A repeatability of better than 10% was obtained on the basis of four independent measurements. The thickness of the sulphur- and phosphorus-rich surface layer formed in the presence of EP additives is much smaller than that of the so-called white layer produced by heavy deformation and a high local temperature. The observed wear-preventive action of the sulphur-rich reaction layer and the possibility of characterizing this layer by AES offer interesting approaches to the study of the mechanism of wear prevention by EP additives.     

Study of the Regenerated Layer on the Worn Surface of a Cylinder Liner Lubricated by a Novel Silicate Additive in Lubricating Oil

Some special silicate particles as additives in lubricating oil have shown a certain self-repairing function for the rubbing pairs of industrial equipment in recent R&D of extreme pressure antiwear additives. This article introduces an investigation on the regenerated layer on the worn surface of a practical cylinder liner lubricated by lubricating oil with a silicate additive using some advanced techniques like transmission electron microscopy (TEM), atomic force microscopy (AFM), nano-hardness tester, scanning electron microscopy (SEM), auger electron spectroscopy (AES), and Raman spectroscopy. The basic formula of the mineral in the silicate additive is Al₄[Si₄O₁₀](OH)₄. Through some macro- and microanalyses, it was found that the silicate additive showed an obvious improving effect on their friction surface and self-repairing function. The roughness of the worn surface could be decreased greatly to several tens of nanometers, and its hardness was still above 10 GPa. The worn surface with some pits and cracks had been covered by a transparent regenerated layer, and the wear of cylinder liners was maintained at almost zero-wear level on average. The mechanism of the self-repairing function was approached. It was revealed that the silicate additive was acting as a catalyst to promote a series of complex tribochemical reactions to form a regenerated layer with amorphous carbon structure on the worn surface under high-friction temperature and pressure in the friction and wear process.