Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.

MICROSTRUCTURE AND MECHANISM OF A NEW TYPE OF Ni－Fe－W－P－S WEAR－RESISTANT BRUSH PLATING LAYER

ＭＩＣＲＯＳＴＲＵＣＴＵＲＥＡＮＤＭＥＣＨＡＮＩＳＭＯＦＡＮＥＷＴＹＰＥＯＦＮｉ－Ｆｅ－Ｗ－Ｐ－ＳＷＥＡＲ－ＲＥＳＩＳＴＡＮＴＢＲＵＳＨＰＬＡＴＩＮＧＬＡＹＥＲＨｕｉＷｅｎｈｕａ（惠文华）ＺｈａｎｇＪｉｎｐｉｎｇ（张瑾平）ＳｈａｏＬｉｗｅｉ（邵力为）...

The Friction and Wear Properties of the Spherical Plain Bearings with Self-lubricating Composite Liner in Oscillatory Movement

A test method based on the condition simulation and a friction and wear test machine featuring in oscillatory movement were set up for self-lubricating spherical plain bearings (SPB). In the machine the condition parameters such as load, angle and frequency of oscillation and number of test cycles can be properly controlled. The data relating to the tribological properties of the bearing, in terms of friction coefficient, linear wear amount, temperature near friction surface and applied load, can be monitored and recorded simultaneously during test process by a computerized measuring system of the machine. Efforts were made to improve the measurement technology of the friction coefficient in oscillating motion. In result, a well-designed bearing torque mechanism was developed, which could reveal the relation between the friction coefficient and the displacement of oscillating angle in any defined cycle while the curve of friction coefficient vs number of testing cycles was continuously plotted. The tribological properties and service life of four kinds of the bearings, i.e, the sampleⅠ-Ⅳ with different self-lubricating composite liners, including three kinds of polytetrafluoroethylene (PTFE) fiber weave/epoxy resin composite liners and a PTFE plastic/copper grid composite liner, were evaluated by testing, and the wear mechanisms of the liner materials were analyzed.

Wear Performance of Ni/ZrO_2 Infiltrated Composite Layer

The Ni/ZrO2 was used as raw materials to fabricate the surface infiltrated composite layer with 1-4 mm thickness on cast steel substrate through vacuum infiltrated casting technology. The microstructure indicated that the infiltrated composite layer included surface composite layer and transition layer. Wear property was investigated under room temperature and 450 ~C. The results indicated that the abrasion volume of substrate was 8 times that of the infiltrated composite layer at room temperature. The friction coefficient of infiltrated composite layer decreased with the increasing load. The wear resistance of infiltrated composite layer with different ZrO2 contents had been improved obviously under high temperature. The friction coefficient of infiltrated composite layer was decreased comparing with that at room temperature. The oxidation, abrasive and fatigue abrasion was the main wear mechanism at room temperature. Oxidation abrasion, fatigue wear and adhesive wear dominated the wearin~ process under elevated temperature.

To a forecasting of the wear-resistance of friction units details parameters question

The process of wear process expedient considering as set of special cases wear. For each special case wear were received settlement with reference to some certain conditions of experimental researches realisation, uniting in self SLOP. For successful application deduced dependence at forecasting wear-resistance the mechanism of reduction is developed which allows to distribute deduced dependencies to any conditions of wear process.

钛合金摩擦磨损性能及减磨方法研究进展

钛合金具有比强度高、抗腐蚀性强、耐高温以及生物相容性好等优点,在汽车制造、生物医疗等众多领域具有重要应用。但钛合金的摩擦磨损性能较差,会影响机械系统的使用寿命和可靠性。首先论述了摩擦磨损过程中摩擦层的形成过程以及摩擦层对钛合金磨损机理的作用,分析了润滑条件、环境温度、滑动速度、载荷等工况条件对钛合金摩擦磨损性能的影响规律。其次,对比总结了钛合金减磨的常见工艺方法及优缺点,指出了当前钛合金磨损机理研究和性能改善方面存在的问题。最后,对今后的研究工作进行了展望:将实验与仿真相结合,阐明钛合金摩擦层和磨损机理的动态变化规律;考虑各种环境因素对钛合金磨损机理的影响,完善钛合金磨损机制图;通过对多种技术协同配合时的工艺参数进行优化,促进钛合金表面强化复合技术的发展,从而提升钛合金的耐磨减摩性能。

热拌极薄抗滑磨耗层在高速公路抗滑性能提升中的应用

为研究热拌极薄抗滑磨耗层在高速公路养护中的应用,提升路面抗滑性能,论文结合实际工程,介绍了热拌极薄抗滑磨耗层工程特性,详细阐述了热拌极薄抗滑磨耗层原材料及配合比设计,重点对热拌极薄抗滑磨耗层施工技术要点进行研究。结果表明:公路养护中采取热拌极薄磨耗层技术进行处理,其路面抗滑性能得到有效提高,并节约养护成本。

42CrMo钢表面激光熔覆钴基金刚石耐磨层组织及性能

目的增强42CrMo钢的耐磨性,改善其严重的磨损失效情况。方法采用激光熔覆技术同步送粉的方式在42CrMo钢表面制备金刚石/WC颗粒增强钴基复合熔覆层,借助SEM、EDS、XRD、显微硬度仪和多功能综合性能测试仪,研究了熔覆层宏观形貌与微观组织、物相组成、显微硬度与耐磨性。结果使用Ti/TiC粉末对金刚石进行预处理可以改善其烧蚀和石墨化;适量ZrH2提升了熔覆层宽厚比,促进了熔池对流传质作用,同时,活性元素Zr改善了金刚石颗粒的润湿性能,提高了黏结相对金刚石的把持力。熔覆层多道搭接过渡均匀,其显微组织主要由细小枝晶及致密网状碳化物共晶组成,熔覆层与基体结合区域反应生成了平面晶组织,进而提高了熔覆层结合强度。激光熔覆热特性使W2C、ZrC、γ-(Co,Fe)、M6W6C、CoZr_(2)、(Ti,Zr)O_(2)、TiCx、Co_(3)Ti等物相存在于熔覆层内,细晶强化及弥散强化作用使得熔覆层的平均显微硬度(1002HV0.2)是基体的3倍。熔覆层平均磨损量是基体平均磨损量的1/2,熔覆层平均摩擦因数也明显低于基体,表明熔覆层的耐磨性能得到提升,其磨损机制主要为磨粒磨损,熔覆层内金刚石因承担摩擦载荷而钝化,但磨痕中的金刚石完整且未发生脱落。结论金刚石/WC颗粒增强钴基复合熔覆层的耐磨性显著提高,可用于42CrMo钢表面强化。

超高速滑动电接触CuCrZr合金轨道表面磨损机制及电接触性能

电磁轨道发射具有典型超高速滑动电接触特性(出口速度大于等于2000 m/s),电磁轨道表面会发生磨损。为研究轨道表面磨损状态与接触电阻之间关系,通过开展电磁轨道发射试验,研究发射后的CuCrZr轨道表面沉积层的形成与磨损机制,揭示枢轨间静态接触电阻的演变规律,总结沉积层的形成与接触电阻的关联关系。结果表明:沿着发射方向,轨道表面沉积层覆盖面积逐渐增大,沉积层的形成机制由摩擦材料转移变为电枢表面熔化飞溅,表面磨损特征由机械磨损向电气磨损转变;由于轨道不同位置沉积层形成原因不同,导致表面粗糙度分布不一致,枢轨间静态接触电阻随接触沉积层形貌特征改变呈现上升、下降及波动3个变化阶段;并且枢轨间静态接触电阻随着接触压力的增大而减小。研究成果对电磁轨道发射装备的研究及发射动力学研究具有理论价值。

冷拌碎石磨耗层在高速公路抗滑性能提升中的应用

为研究冷拌碎石磨耗层在高速公路抗滑性能提升中的应用,结合实际工程,介绍了冷拌碎石磨耗层、纤维超黏磨耗层、极薄磨耗层和超薄磨耗层4种路面抗滑性能提升处治技术,重点对冷拌碎石磨耗层施工技术要点进行研究,并对其施工质量进行检测。

钢渣多孔超薄磨耗层混合料路用及抗松散性能研究

为研究钢渣多孔超薄磨耗层混合料路用及耐久性能,采用钢渣替代2.36 mm以上的玄武岩粗骨料,并设计了18%、21%和24%三种空隙率制备多孔超薄磨耗层混合料,分别采用高温车辙、低温小梁弯曲、冻融劈裂强度、水渗透仪等试验研究了钢渣多孔超薄磨耗层混合料的高温稳定性、低温抗裂性、水稳定性、渗水性等路用性能,并进行了不同环境条件下的肯塔堡飞散试验,评价多孔超薄磨耗层混合料在标准、高温和冻融条件下的抗松散性。结果表明,添加钢渣增强了混合料内部骨料之间的嵌入和挤压效果,强化了钢渣与沥青之间的物理和化学吸附作用,增强了混合料的内聚力,使得其在高温稳定性,低温抗裂性、水稳定性和排水性能等方面较玄武岩混合料分别提高了140%、4.1%、7.1%和1.6%;随着空隙率的增大,钢渣多孔超薄磨耗层混合料的相关路用性能除了排水性,均有所下降;肯塔堡飞散试验结果表明钢渣的掺入提高了沥青用量,且增强了骨料的插层性,从而获得更好的抗松散性,但随着空隙率由18%增至24%,钢渣混合料标准飞散损失增大了41.8%,标准条件下测得的质量损失都小于高温或冻融条件,且高温条件下的水分损伤评价效果优于冻融循环条件。

熔覆电流对铁基TiC耐磨层组织与性能的影响

为研究等离子熔覆电流对铁基TiC耐磨层组织和性能得影响,分别制备了熔覆电流为140 A、160 A、180 A和200 A的铁基TiC耐磨层,并对其微观形貌、显微硬度及耐磨粒磨损性能进行了表征分析。结果表明:耐磨层显微硬度先增加后减小,而磨损失重量呈逐渐增加趋势。熔覆电流为140 A时,耐磨层耐磨损性最好,显微硬度HV达755,可获得较好的综合性能。

15×K6-EPIWRC多层阻旋转抗冲击钢丝绳研制

多层压实股钢丝绳阻旋转性能在一些应用场合有极其重要的意义,钢丝绳旋转超过相关要求会影响工作效率,甚至产生安全事故。为最大限度地克服阻旋转性差、断芯、外层磨损超标3大难题,新产品采用1-4+4/15结构形式,对绳芯进行注塑处理,以满足客户要求。26.0 mm钢丝绳研制完成后,实际破断拉力达到681.0 kN,钢丝绳各项指标均达到客户标准和EN12385标准要求,工艺设计合理,绳捻制紧密,抗旋转性能优良,抗冲击载荷性能好。

窄孔内壁激光金属沉积Stellite6合金耐磨层组织及性能研究

为解决窄孔内壁堆焊的可达性差和提高304L不锈钢的耐磨性能,采用激光金属沉积的方式在深30 mm、直径14 mm的304L窄孔内壁制备了一层约2.5 mm厚、致密度为99.9981%、无裂纹、未熔合等缺陷的stellite6耐磨层。通过微纳CT、XRD、金相、硬度测试和摩擦磨损试验等方法,系统研究了耐磨层的组织、相组成、硬度分布和耐磨性能。结果表明,Stellite6耐磨层致密无缺陷,其显微组织从底部到顶部依次为平面晶、胞状晶、树枝晶和等轴晶。相组成主要为γ-Co、M_(23)C_(6)、CoCx及(Cr,Fe)_(7)C_(3)等。熔合线附近各种元素均匀分布,未出现明显聚集。耐磨层的显微硬度平均值是基体304L的2.38倍,且窄孔不同高度位置的显微硬度值相对稳定。耐磨层的磨损率较304L基体降低了29.3%,显示出优异的耐磨性能。该研究为大深宽比内孔壁激光金属沉积耐磨层在核电、能源动力等行业的应用提供了依据。

不同高黏剂对排水沥青磨耗层路用性能的影响

采用不同高黏改性剂对SBS改性沥青进行改性获得高黏改性沥青,通过高温车辙、低温小梁弯曲和冻融劈裂试验对不同高黏改性排水沥青磨耗层的高温、低温和水稳性能进行研究。结果表明,高模量剂B对SBS改性沥青的改性效果最佳,高模量剂B改性沥青60℃动稳定性达到11665次/mm,弯曲破坏应变为3862uε,冻融劈裂残留强度比为91.5%。

彩色沥青路面抗滑磨耗层路用性能研究

为了提升彩色沥青路面抗滑磨耗层的路用性能,文章以环氧树脂胶结料和玄武岩碎石为试验对象,在实验室条件下,模拟了玄武岩不同撒布量对彩色沥青路面抗滑磨耗层的高温稳定性、低温抗裂性、水稳定和抗滑性能等路用性能的影响,试验结果表明:随着玄武岩撒布量的增加,彩色沥青路面抗滑磨耗层的路用性能表现出先增大后减小的变化趋势,当玄武岩撒布量达到70%时,彩色抗滑磨耗层的路用性能表现最优。

Sliding Wear of the Hybrid Kevlar/PTFE Fabric Reinforced Phenolic Composite Filled with Nano-titania

The Kevlar/polytetrafluroethylene（Kevlar/PTFE） fabric composite can be used as a self-lubricating liner of the self-lubricating bearing.Many types of nano-particles can improve the tribological performance of the polymer-based composite.Unfortunately,up to now,published work on the effect of nano-particles on the tribological performance of the fabric composite which can be used as a self-lubricating liner is quite scarce.Therefore,for the purpose of exploring a way to significantly improve the tribological performance of the fabric composite,the tribological performance of the Kevlar/PTFE fabric composite filled with nano-titania is evaluated by using the block-on-ring wear tester.The scanning electron microscopy is utilized to observe the morphologies of worn surfaces of the fabric composites and the counterparts.The tensile properties of the composites are evaluated on the universal material testing machine.The test results show that the addition of nano-titania at a proper mass fraction of the matrix resin improves the wear resistance and the tensile strength,decreases the friction coefficient,and makes the wear volume of the composite reach a relative steady state more quickly;plastic deformation and microcutting are important for the wear of the fabric composite;a lubricating layer is formed on the worn surface of the composite during sliding,and the lubricating layer is critical for the tribological performance of the composite;the formation and properties of the lubricating layer are influenced by the nano-titania particles.The proposed study on the effect of nano-titania on the tribological performance of the Kevlar/PTFE fabric composite,especially on the evolution of the worn surface of the composite,provides the basis for further understanding of the influence mechanism of the nano-particles on the tribological performance of the composite and explores a method of improving the tribological performance of the composite.

Microstructures and properties of the nitrided layers fabricated on titanium substrate by direct current nitrogen arc melting technique

The nitrided layers mainly containing TiN dendrites were fabricated by direct current nitrogen arc melting method. The test results show that the layers are harder and more resistant to wear than the titanium substrate. Arc traveling speeds and arc currents have an effect on both the microstructures and the properties of the layers. Decreasing the arc traveling speed or increasing the arc current can obviously enhance the hardness and the wear resistance of the nitrided layers.

Evaluation of Microstructure and Wear Properties of Ti-6Al-4V Alloy Plasma Carbonized at Different Temperatures

Ti-6A1-4V （TC4） alloys were plasma carbonized at different temperatures （900, 950, and 1 000 ℃） for duration of 3 h. Graphite rod was employed as carbon supplier to avoid the hydrogen brittleness which is ubiquitous in traditional gas carbonizing process. Two distinguished structures including a thin compound layer （carbides layer） and a thick layer with the mixed microstructure of TiC and the a-Ti in carburing layer were formed during carburizing. Furthermore, it was found that the microstructure and the properties of TC4 alloy were significantly related to the carbonizing temperature. The specimen plasma carbonized at 950 ~2 obtained maximum value both in the hardness and wear resistance.

Friction and wear behaviors of Al_2O_3-13 wt% TiO_2 coatings

Abstract Nanostructured and conventional AlzO3- 13 wt%TiO2 coatings were manufactured by air plasma spray. Friction and wear behaviors of coatings were investigated at room and elevated temperatures using an SRV wear test machine. The nanostructured coating has ＂two regions＂ microstructure, while the conventional coating has typical layered microstructure with obvious interfaces among splats. The coefficient of friction decreases with rising of temperature because of the for- mation of tribo-layer at elevated temperatures. The wear resistance of the nanostructured coatings is higher than that of the conventional coating, and the wear threshold of applied load is 30 N for conventional coating and 40 N for nanostructure coating. The wear resistance difference is related to the ＂two regions＂ microstructure of nanostruc- ture coating, which could blunt or branch the cracks propagation. In our test ranges, the wear rates rising are more sensitive with the applied wear load rising than with the temperature rising.