Comments on process of duplex coatings on aluminum alloys

Despite the great achievements made in improvement of wear resistance properties of aluminum alloys,their applications in heavy surface load-bearing are limited. Single coating is insufficient to produce the desired combination of surface properties. These problems can be solved through the duplex coatings. The aim of the present study is to overview the research advances on processes of duplex coatings on aluminum alloys combined with micro plasma oxidation process and with other modern processes such as physical vapour deposition and plasma assisted chemical vapour deposition and also to evaluate the performance of micro plasma oxidation coatings in improving the load-bearing, friction and wear resistance properties of aluminum alloys in comparison with other coatings. Wherein, a more detailed presentation of the processes and their performances and disadvantages are given as well.     

Lubricating properties of polyalkylene glycol and organic phosphate ester mixed aqueous solutions

Till now,water based lubricants,especially aqueous solutions,have not been employed in the elastohydrodynamic lubrication(EHL)due to their poor film forming capability or low wear resistance.In this paper,we proposed a method to develop water based lubricant:employing polyalkylene glycol solution as base stock to improve EHL film forming capability and using organic phosphate ester(DPZ)as anti-wear additive to improve wear resistance property.The lubricating properties of the mixed solutions,including load carrying capability,wear resistance property,friction reduction property,EHL film forming behavior,were investigated.The experimental results indicate that the mixed solution presents excellent lubricating properties,which make it a promising candidate in developing water based lubricants.     

Double Glow Plasma Hydrogen-free Carburizing on Commercial Purity Titanium

A carburized layer with special physical and chemical properties was formed on the surface of commercial purity titanium by a double glow plasma hydrogen-free carburizing technique,High-purity netlike solid graphite was used as a raw material and commercial purity titanium was used as the substrate material.Argon gas was used as the working gas.The carburized layer can be obviously observed under a microscope.X-ray diffraction indicates that TiC phase with higher hardness and dissociate state carbon phase was formed in the carburized layer.The glow discharge spectrum（GDS） analysis shows that the carbon concentration distributes grodiently along the depth of carburized layer.The surface hardness of the substrate increases obviously.The hardness distributes gradiently from the surface to inner of carburized layer.The friction coefficient reduces by more than 1/2,the ratio wear rate decreases by above three orders of magnitude.The wear resistance of the substrate material is improved-consumedly.     

MODIFICATION OF FLAKE REINFORCED FRICTION BRAKE COMPOSITE MATERIAL

According to the recent development trend and need of the friction brake material, the flake reinforced friction brake material has been made out by adjusting the recipe and techniques.The two-dimensional flake vermiculite is selected as the reinforced stuffing of the material; the modified resin is used as the basal bed of the material.The tests manifest that the properties of mechanics are high, the friction coefficients are suitable and stable,and especially in high temperatures the wear is low.It is an excellent friction brake material.     

Relationship among wear-resistance of three-body abrasion, substructure and property in martensite steels

The effects of subsurface hardness on wear-resistance of martensitic steel 20Cr, 40CrSi, 60Mn, T8 and T10 in three-body abrasion under static load was investigated. It shows that the characteristic of the subsurface hardness distribution and the abrasive wear resistance is related to the substructure near the worn surface. The substructure of the tested martensite steel has an apparent relationship with the carbon content and steels with moderate carbon content and hardness exhibit good resistance to abrasive wear. The competition of the work-hardening effect and the temper softening effect, which resulted from deformation and friction heat generating during abrasive wear is considered to be a main reason for the relation among wear-resistance, hardness and substructure. At the test conditions, the wear-resistance of 40CrSi is the best.     

LPCS Ni-Zn-Al2O3 Intermediate Layer Enhanced SPS NiCr-Cr3C2 Coating with Higher Corrosion and Wear Resistances

The double-layer NiCr-Cr₃C₂/Ni-Zn-Al₂O₃ coatings with sufficient corrosion and wear resistance were prepared on low carbon steel substrates.The intermediate layers Ni-Zn-Al₂O₃ were fabricated by using low-pressure cold spray (LPCS) method to improve the salt fog corrosion resistance properties of the supersonic plasma spray (SPS) NiCr-Cr₃C₂ coatings.The friction and wear performance for the double-layer and s...     

Hemocompatibility of DLC coatings synthesized by ion beam assisted deposition

Ion beam-assisted diamond-like carbon (DLC) coatings have been used for growing the human platelet, fibrinogen, and albumin in the control environment in order to assess their hemocom-patibility. The hard carbon films were prepared on polymethylmethacrylate (PMMA) at room temperature using ion beam assisted deposition (IBAD). Raman spectroscopic analysis proved that the carbon films on PMMA are diamond-like with a higher fraction of sp3 bonds in the structure of mixed sp2 + sp3 bonding. The blood protein adsorption tests showed that DLC coatings can adsorb more albumin and are slightly more fibrinogen than the PMMA chosen as a control sample. The platelets adhered on DLC coatings were reduced significantly in number. These results indicate good hemocompatibility of DLC coatings.     

Tribological Characteristics of Chromium-active Carbon Electroplated Composite Coatings

A process of chromium electroplating using a standard bath with additives and active carbon particles was reported, and the tribological behaviors of the composite coatings using the pin-on-disk tester and the table wear tester were i nvestig(aed. Experimental results indicate that the electroplated chromium-active carbon composite coatings exhibited the low friction coefficient anti excellent anti-wear properties whets coffered with the normal chromium electroplated ones. The formation of active carbon particles within the chromium matrices can be explained by SEM analysis and the mechanis of wear resistance of the composite coatings were studied.     

Bionic surface design of cemented carbide drill bit

The development of a high-performance cemented carbide drill bit is of great significance to the reduction of rock drilling-cost. The non-smooth features of a biological surface provide an insight into how they can obtain low friction and good wear resistance with evolving surface morphology. By analyzing the mechanism of the surface of a dung beetle for reducing soil wear and adherence, we design a cemented carbide drill bit with a bionic surface, which is expected to have superior anti-wearing and anti-sticking properties for drilling the soft coal seam. Inspired from the characteristics of the head and pronotum surface of the dung beetle, optimized non-smooth surface of the drill bit was constructed. The working performance of this innovative drill was experimentally tested. With comparative experiments under the identical drilling conditions, the wear rates, drilling times of conventional drills and bionic drills were measured. Compared with the conventional counterpart, the drill designed exhibits better performance in reducing wear and sticking drilling-breaks, therefore achieving higher levels of efficiency. The diameter of the dome and pit on the bit surface is in the range of 0.8–1.2 mm, and the bionic drill bits could get better performance with preferable drilling speeds and wear rates.     

Tribological Properties of MoSi2 Against AISI10045 Steel Under Sliding Friction

MoSi2 samples were prepared by a self-propagating high-temperature synthesis （SHS） and a hot-press technique. The sliding friction and wear properties of intermetallic MoSi2 against AISI10045 steel under dry friction and oil lubrication conditions were investigated with a MRH-5A type ring-on-block friction and wear tester. The elemental composition, microstructure and worn surface morphology of the MoSi2 material were observed and analyzed by means of scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The synthetic parameter pv value reflecting friction work, was used to discuss the tribological properties of MoSi2 material. The results show that 1） oil lubrication can obviously improve the tribological properties of MoSi2, 2） the bigger the pv value, the greater the antifriction and the abrasive resistance of MoSi2 under oil lubrication, 3） with an increase in the pv value, the wear mechanism of MoSi2 material under dry sliding friction is the fatigue fracture and adhesive wear and 4） under oil lubrication the wear mechanism is mainly fatigue pitting.     

不锈钢(3Cr13)镀类金刚石薄膜的研究

利用脉冲真空电弧离子镀技术在3Cr13不锈钢基底上制备类金刚石(DLC)薄膜,采用X射线光电子能谱技术分析DLC薄膜中sp3键及sp2键含量和组分.采用显微硬度计测试了薄膜的显微硬度,利用扫描电镜测试了膜的表面形貌.划痕仪测试了薄膜与不锈钢基底的结合强度.结果表明:所镀制的类金刚石薄膜品质优良,类金刚石中sp3键含量较高,sp3/sp2=1.63,具有良好的表面形貌,在不锈钢上沉积DLC膜后明显提高了不锈钢的硬度,Ti过渡层的引入明显的改善了膜与不锈钢之间的结合强度.     

脉冲真空电弧离子镀沉积类金刚石薄膜的结构和力学性能研究

利用脉冲真空电孤离子镀技术在3Cr13不锈钢上制备了类金刚石(DLC)薄膜．通过Raman光谱分析了膜的结构特征，采用摩擦磨损试验机测试了薄膜在不同载荷下的摩擦系数，运用划痕仪研究了膜基的结合强度．结果表明：所镀制的薄膜具有典型类金刚石结构特征，膜中ID／IG为1．33；摩擦系数随着载荷的增大而减小，载荷为5N，转速120r／min时的摩擦系数为0．02；Ti过渡层的引入显著地提高了膜基结合力．     

Plasma preparation method and tribological properties of diamond-like carbon coating on magnesium alloy AZ31 substrate

Magnesium alloys are light weight and exhibit good recyclability but suffer from low hardness and wear resistance.In this study,the hardness and wear resistance of AZ31 magnesium alloy were improved by depositing diamond-like carbon(DLC)films as hard protective coatings using ion-beam-enhanced deposition with various CH_4/H_2 ratio,gas flow rates and accelerating voltages.The supporting effect of the magnesium alloy was enhanced by the production of a graded interfacial layer which is composed of film atoms and substrate atoms.The composition and mechanical properties of the DLC coatings were characterized using scanning electron microscopy(SEM),Raman spectroscopy,Rockwell test and nano-indentor.The tribological properties of the coating were also investigated using a frictional surface microscope with an in situ observation system and friction force measurements.The DLC films were characterized by a lower intensity ratio of the D-peak to G-peak(I_D/I_G),higher hardness,and improved tribological properties when deposited at a lower accelerating voltage(6 kV).At the CH_4/H_2 ratio of 1:99 and 6 sccm/6 kV,minimum I_D/I_G values of 0.62,relatively low friction force value of 0.12 N,and a maximum hardness of 4056HV were attained respectively.In addition,the DLC film exhibited improved wear resistance and a shallower wear track at this condition.     

类金刚石薄膜挺柱的制备与性能

采用磁控溅射的方法,利用氩气和甲烷为气源,在中国第一汽车股份有限公司自主研发的发动机配气机构的挺柱上制备类金刚石(DLC)薄膜。利用摩擦磨损试验机和发动机配气机构试验台架,研究了DLC涂层挺柱的摩擦学行为及其对发动机节能的影响。试验结果表明,在边界润滑条件下,DLC涂层挺柱的摩擦因数比原零件降低67%,抗磨损性能大幅度提高;在实际使用工况下,配气机构的摩擦损失降低6%。DLC涂层零件可以降低发动机摩擦损失,适用于汽车低碳技术路线。     

改变过渡层碳靶功率在铜上沉积类金刚石膜的研究

类金刚石膜具有硬度高、 摩擦系数低、 耐腐性强、 稳定性高等优点, 是提高铜耐腐性的理想材料, 但铜 与类金刚石膜之间的结合力差。通过制备T i xC y 过渡层, 采用磁控溅射物理气相沉积与化学气相沉积法, 通过改变 过渡层碳靶功率成功在铜基体上沉积类金刚石膜。并对金刚石膜进行拉曼光谱测试、 划痕实验和电化学实验分析。 结果表明, 所制备碳膜具有典型的类金刚石结构, 膜与基体之间的结合强度大, 过渡层碳靶溅射功率为2 0 0W 时所 制备的类金刚石膜对铜基体的保护作用最好。     

Extraordinary self-lubrication properties of non-hydrogenated diamond-like carbon films under humid atmosphere

Tribological properties of non-hydrogenated diamond-like carbon (DLC) films were investigated under humid (RH=80%) and dry (RH=5%) air. These films were deposited by pulsed laser deposition (PLD) at different substrate temperatures. Tribological properties of DLC fabricated by PLD is not sensitive to the relative humidity of testing environment. Because of the unique growth mechanism of DLC prepared by PLD, DLC is of “soft-hard” double layers, having a very low friction coefficient and wear rate under humid atmosphere. The minimum coefficient and wear rate of film under humid circumstance are 0.045 and 5.94×10⁻¹⁰ mm³N⁻¹m⁻¹, respectively, just a little bit more than those under dry condition. The root means square roughness of film is less than 1 nm. The sp³ content of film grown at room temperature (RT) is 72%, and the sp³ content decreases with temperature. Raman spectrum shows that the micro-structure is amorphous network. The largest hardness and elastic modulus of film are 51 GPa and 350 GPa, respectively and they reduce with increase of deposition temperature too. Water contact angles on surface are more than 90° which indicates that films fabricated by PLD are hydrophobic with low surface energy.     

H2对类金刚石薄膜性能影响的研究

类金刚石膜因其高的硬度、高的介电性、低的摩擦系数、优异的光学和化学性能以及巨大的潜在应用前景而成为研究热点。采用离子增加化学气相沉积方法在Si基底表面制备含氢类金刚石薄膜,通过XPS能谱测试,确定膜层的成份组成,膜层中除了含有碳以外还含少量的吸附的氧。调节反应源气体中H：的比例,结果表明H2的含量直接影响DLC薄膜的性能。随着H。的含量增大,膜层的表面粗糙度降低,膜层的硬度变大,而应力相应增大。这是由于反应源气体中H2含量的增加,DLC薄膜中氢的含量反而降低,膜层内sp2团簇结构的无序性增加,sp2键的比例增加,这将使得膜层内的碳的空间网络结构所占的比例增加。     

类金刚石薄膜电极在污水处理中的应用

以类金刚石(DLC)薄膜作为电极进行污水处理时,具有比IrO2/Ta2O5钛涂层电极、PbO2等电极更好的氧化效果,这是由于DLC具有更宽的电势窗口和更低的背景电流.此外,DLC还具有耐酸、耐腐蚀以及低吸附特性等特点,不会在酸性、腐蚀性的污水中破损,因此比其他的电极更适合在污水中长时间工作.为此,对DLC的制备、DLC电极电化学性能的影响参数,以及DLC在污水处理中应用的研究成果进行了综述总结.     

射频磁控溅射制备类金刚石薄膜

采用射频磁控溅射法在Si和Ti合金基体上沉积出类金刚石(DLC)薄膜.利用拉曼光谱仪、划痕仪和扫描电子显微镜分析了DLC薄膜的结构、膜基附着力和表面形貌.结果表明:射频磁控溅射法能够制备出表面平整、结构致密的DLC薄膜;同时基体材料的不同不会影响DLC薄膜的键合结构,Si基体上涂层附着力为30N,Ti基体上膜基结合力大于40 N.     

金属-类金刚石薄膜研究进展

类金刚石膜中的金属粒子可缓解类金刚石薄膜中由于制备态产生大内应力而导致的膜厚受限这一矛盾,能显著改变薄膜各种性能.述评了金属-类金刚石薄膜的制备工艺、不同金属粒子对DLC薄膜形态、键结构、力学及摩擦磨损性能、物理化学性能等的影响,指出在金属粒子对DLC膜的力学及摩擦学性能的影响方面还有很多待确定的因素.