Characteristics of the Worn Surface of Magnetized Sliding Contact Medium Carbon Steel/Medium Carbon Steel

The characteristics of the worn surface of a pin were studied in the presence of a DC magnetic field. The experiments were conducted on a pin-on-disk tribometer in the ambient atmosphere. The medium carbon steel/medium carbon steel sliding couple was adopted. Compared to the pin formed in the absence of a magnetic field, oxidation becomes visible on the worn surface of the pin during the process of friction with the action of magnetic field. Fe₂O₃ was detected from the worn surface of a pin in the stable wear stage. The oxidation area of the worn surface of the pin gradually extends with increasing friction time. The wear of the pin decreases with extending of the oxidation area on the worn surface of the pin. The results reveal that the oxide layer formed on a pin worn surface is one of the key antiwear factors in the presence of a magnetic field.     

Wear and Friction Characteristics of Magnetorheological Fluid under Magnetic Field Activation

In this article, wear and friction characteristics of a magnetorheological (MR) fluid were studied under different magnetic fields. Using a pin-on-disc tribometer, the wear loss and friction coefficient were obtained with and without a magnetic field. The friction and wear of three typical materials under magnetic field were investigated at various normal loads and rotating speeds. After the wear tests, the worn surfaces of specimens were observed using a scanning electron microscope (SEM) in order to investigate the wear mechanisms, and the contacting surfaces were analyzed by energy-dispersive X-ray spectroscopy (EDS) to investigate the variation of elemental composition on the worn surface. Test results showed that the MR fluid exhibits better tribological characteristics under a magnetic field compared to the case without a magnetic field. The general morphology of the MR particles and wear debris was observed to assist with the analysis of friction and wear. The SEM micrographs and EDS spectra of the worn surfaces showed that the predominant wear mechanism in the case of the steel and brass specimens was abrasive wear by asperities and MR particles on the worn surfaces, whereas a mixed wear mechanism that included adhesive wear and abrasive wear was observed in the case of the aluminum specimen.     

Frictional Properties and Mechanisms of an Organic–Metal Brake Pair Braking Repeatedly in Magnetic Field

With the aim to investigate repeated braking of organic–metal brake pairs, tribological and scanning electron microscopy (SEM) experiments were performed to reveal the influence of a magnetic field on the tribological performance of brakes. A nonasbestos copper-based brake pad and gray cast iron brake disc were selected as the brake pair. The X-DM pad-on-disc friction tester was improved to set up a tribological tester under a magnetic field. The worn surfaces were observed by SEM to reveal the friction mechanisms. It was found that a magnetic field can ameliorate the dynamic friction and wear. In addition, the global mean friction coefficient increases and the wear resistance of brake materials improves. A magnetic field promotes surface oxidation and aggravates the surface heat emission condition. As a result, the mean temperature on the friction surface increases obviously. An appropriate magnetic field can improve the dynamic temperature rise and decrease the global temperature rise on the friction surface. It is considered that a magnetic field has important influences on tribological performance in repeated braking. Therefore, this research could provide theoretical references for studying the tribological performance in repeated braking and/or under a magnetic field.     

The Effects of Magnetic Treatment on the Tribological Behavior of AISI 1045 Steel under Lubricated Conditions

The mechanical and tribological properties of pulse-magnetized and untreated AISI 1045 steel were studied comparatively. The microhardness and microstructures of treated and untreated steel samples were analyzed to evaluate magnetic treatment effects on the mechanical properties. Dislocation densities were calculated from X-ray diffraction data according to the Williamson-Hall method. Tribological tests were conducted using a ball-on-disk reciprocating friction and wear tester. Scanning electron and energy-dispersive microscopies were used to analyze the morphologies and elements of worn surfaces. Dislocation densities of AISI 1045 steel were found to increase by 16.5% after magnetic treatment. Treated steel performed better under polyalphaolefin (PAO) base oil lubrication with each of five additives, especially when oleic acid was 0.2 and 1.5% (by mass), and the wear scar width and friction coefficient of treated samples were 46.9 and 16.4% lower than those of the untreated samples, respectively. Morphological analyses indicated that micromagnetic fields generated during friction tests not only promoted oxidation of the worn surface and debris but also produced thinner tribofilms that included chemical and adsorbed films.     

外加电磁场对金属材料摩擦副摩擦学性能影响的研究进展

外加电磁场是改善摩擦副摩擦学性能的途径之一。从外加电磁场对位错运动的促进、接触表面氧化的增强和磨屑的细化氧化3个方面,综述了电磁场对金属材料摩擦副摩擦学性能改善的机理,介绍了外加电磁场类型、磁场强度、磁场施加方向、磁场频率以及摩擦副材料的磁导率大小及差异、外加磁性颗粒尺度对摩擦副摩擦磨损的影响,指出了未来电磁场抗磨减摩的研究方向。     

The structure and tribological behavior of nanocomposite carbide coating on steel 45

It is shown that fullerene black interacts with the steel 45 surface and forms a nanocomposite coating including orthorhombic iron carbide Fe₃C with crystallites sized 100–150 nm and dispersed spots of fullerene black with particles sized 40–50 nm. Tribotests show the coefficient of friction of the composite coating to be three-four times lower and the wear resistance about two times higher than these parameters for original annealed steel 45. It is proved that in friction, frictional transfer occurs of hard high-disperse wear products of the coating carbide base and fullerene black to the counterbody, which encourages the decrease in the friction of the pair with one of its elements coated with Fe₃C-fullerene black. The causes of the improved tribological behavior of the carbide coating are discussed.     

Wear behaviour in the presence of magnetic fields for pin-on-disc repeated dry wear tests

Wear behaviour in a magnetic field is discussed for pin-on-disc repeated dry wear tests.The results showed that the sliding distance corresponding to a severe-mild wear transition decreased with increasing magnetic flux density. Consequently, the degree of wear also decreased in the presence of a magnetic field. These phenomena were observed, remarkably, for the case using a carbon steel pin, which is a material that easily oxidizes. To discuss the above phenomena, the oxidation of steel filings in a magnetic field was investigated at high temperature. As a result, it was certain that the activation energy for oxidation decreased both in ac and dc magnetic fields. EPMA observations also proved that the magnetic field promoted oxidation.It was concluded that the degree of wear decrease was caused by magnetic-field-promoted oxidation of wear particles and these oxidized fine wear particles existed and attached to the wear surface owing to the magnetic forces present.     

Studying wear resistance of carbon steels strengthened by plasma hardening

The wear resistance of carbon steels strengthened by plasma hardening in an UDGZ-200 setup is studied using a friction machine. It has been found that the wear resistance of hardened low-carbon steel 15 is equal to ～70% of normalized steel 45, as well as the wear resistances of the hardened medium-carbon steel 45 and the hardened high-carbon U8A steel exceed the wear resistance of the normalized steel 45 by ～60 and ～90 times, respectively.     

石墨干膜润滑剂在碳钢表面摩擦磨损性能试验研究*

传统油或脂润滑剂在极端工况环境下无法满足碳钢类零件的减摩要求,采用干膜润滑剂是提高极端工况环境下碳钢表面摩擦磨损性能的可行性方法。采用超声波分散方法制备以石墨粉末为基体的干膜润滑剂,使用压力喷涂技术使其沉积在碳钢试件表面,在端面摩擦试验仪中开展干摩擦和石墨干膜润滑剂润滑下摩擦磨损性能对比性试验研究。试验结果表明：石墨干膜润滑剂在碳钢表面的沉积效果较好,沉积的石墨干膜润滑剂具有较好的润滑性能,可以有效地保护碳钢表面不被过度磨损;喷涂石墨干膜润滑剂的碳钢试件的工作寿命随着压力载荷和主轴转速的增大而缩短,负载和滑动速度的联合作用会加速涂层向稳定方向的过渡;磨损过程中形成的微观润滑剂颗粒会形成颗粒流润滑,适当添加石墨颗粒粉末可能会延长润滑剂正常发挥减摩作用的时间。制备的石墨干膜润滑剂为碳钢在极端工况环境下的减摩提供了支持。     

直流稳恒磁场对45~#钢磨损性能的影响

大气条件下,研究了低强度直流稳恒弱磁场对45#钢干滑动磨损性能的影响.结果表明:与无磁场条件下相比,直流稳恒弱磁场使45#钢磨损量明显减少;随着磁场强度的增加,磨损量逐渐减少.3-D表面形貌分析表明,施加一定强度磁场的试样磨损后,表面光滑平整.     

GCr15及G20CrNi2Mo轴承钢高温润滑条件下摩擦磨损性能

为了探究轴承钢在高温润滑条件下的摩擦磨损性能,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、洛氏硬度计等对GCr15高碳轴承钢和G20CrNi2Mo渗碳轴承钢组织、物相及硬度进行了表征,利用QG-700型气氛高温摩擦磨损试验机研究轴承钢材料不同条件下的高温润滑摩擦磨损性能,并分析其磨损机制.结果表明:2种轴承钢...     

镀镍石墨磁性纳米粒子对ZL109微弧氧化反应过程及膜层耐磨性能影响

为进一步探索微弧氧化反应过程中微弧氧化陶瓷层表面形貌、孔隙率等基本特征的受控机制,创新地提出向微弧氧化电解液中引入磁性粒子,即镀镍石墨磁性纳米粒子,探索磁性添加剂粒子对微弧氧化反应过程及膜层耐磨性能的影响.从膜层表面形貌、横截面形貌、孔隙率、平均孔径、厚度、表面粗糙度、反应能耗及物相组成等方面对微弧氧化反应过程进行了分...     

Tribological properties of metal-plastic multilayer composites under oil lubricated conditions

Three kinds of metal-plastic multilayer composites, which were composed of a steel backing, a middle layer of sintered porous bronze and a surface layer of polytetrafluoroethylene (PTFE) filled by Pb or Cu₂O powders, were prepared. The friction and wear properties as well as the limiting pressure times velocity (PV) values of these metal-plastic multilayer composites sliding against 45 carbon steel under both dry and oil lubricated conditions were evaluated on a MPV-1500 friction tester with a steel axis rotating on a journal bearing. The worn surfaces of these metal-plastic multilayer composites and the transfer films formed on the surface of steel axis were examined by electron probe microscopy analysis (EPMA). Experimental results show that filling of Pb to PTFE reduces the friction coefficient and wear of the composite, while filling of Cu₂O to PTFE increases the friction coefficient but decreases the wear of the composite. The friction and wear properties as well as the limiting PV values of these metal-plastic multilayer composites can be greatly improved with the oil lubrication. EPMA investigations show that Pb and Cu₂O fillers preferentially transfer onto the surfaces of steel axis, which may enhance or deteriorate the adhesion between transfer films and steel surfaces. Meanwhile the transfer of these metal-plastic multilayer composites onto the steel surface can be greatly reduced with oil lubrication, which results in the remarkable decrease of the wear of these metal-plastic multilayer composites.     

硅酸盐粉体作为润滑油添加剂在金属磨损表面成膜机制

在润滑油中添加蛇纹石硅酸盐粉体,采用MM-200摩擦磨损试验机研究了45#钢-45#钢摩擦副磨损表面的自修复陶瓷膜层形成机制,借助SEM及EDAX测试分析自修复陶瓷膜层的表面形貌及表面成分组成。结果表明摩擦能量对硅酸盐添加剂在磨损表面形成自修复膜层有很大的影响:自修复膜层为氧化物陶瓷材料,主要成分来自于硅酸盐添加剂。在低载荷300 N时,摩擦因数减小,硅酸盐添加剂不能转移到磨损表面,不能形成自修复膜层,仅仅起到减磨作用。下试样的失重随磨损时间增加而增加;在试验时间为20 h时,试样失重达到最大值,随后试样的失重反而减小。在载荷为600 N、900 N,试验时间30 h摩擦磨损后,在金属表面形成自修复保护膜,磨损表面比较平整光滑,无明显的片层剥落和犁沟,摩擦发生在自修复陶瓷材料之间,摩擦因数增加。硅酸盐添加剂在机械剪切作用下变形,在金属的磨损表面上铺展,并且在摩擦磨损过程中不断向摩擦表面转移,形成了均匀光滑的自修复膜层。自修复膜层隔离了金属摩擦表面的直接接触,摩擦磨损发生在自修复膜层之间,有效地降低了金属的磨损。     

磁场干涉对不同磁属性材料干摩擦学特性的影响

提出并比较系统地研究不同磁属性材料自、互配副在磁场干涉下的干摩擦学特性,定义磁场干涉因子的公式,分析材料磁性与磁场影响程度的关系。结果表明：总体上,磁场干涉下,材料的干摩擦学特性与其磁导率有一定的对应关系,受磁场的影响程度随磁导率的增大而增大;配副材料的磁导率相差太大时,不利于发挥磁场的耐磨减摩效果;由于受各材料化学性能(成分)、力学性能和导热性能不同以及选配的影响,具有明显的系统依赖性;随着磁场的增大,在磨损率方面,铁磁性材料的磨损率有减小的趋势,抗磁性材料的磨损率有增大的趋势;对于顺磁性材料,当与高磁导率的铁磁性材料配副时,磨损率有增大的趋势,而与抗磁性材料配副时,磨损率有略微减小的趋势;在摩擦因数方面,含铁磁性材料的摩擦副的摩擦因数有减小的趋势,含抗磁性材料又不含铁磁性材料的摩擦副的摩擦因数却有增大的趋势。通过对环试样磨损率的分析得出,试样装卡装置的磁性会对试验结果造成一定影响;通过作为环试样的抗磁性锌黄铜磨损率有降低的趋势得出,在抗磁性锌黄铜背面添置铁磁性材料,即可克服磁场对抗磁性材料耐磨性能有不利影响。     

MoDTC增强型磁性液体减摩性能试验研究

为提高磁性液体的减摩性能，在现有Fe3O4磁性液体的基础上，通过微量添加二烷基二硫代氨基甲酸钼（MoDTC），制备一种MoDTC增强型磁性液体。对MoDTC增强型磁性液体微观粒子的结构、组成成分、磁性能进行测试分析，在不同载荷、速度条件下进行摩擦磨损试验，探究MoDTC含量对磁性液体摩擦磨损性能的影响。实验结果表明：MoDTC增强型磁性液体比铁磁性液体饱和磁化强度小，且剩磁几乎为0，具有较好的磁性能；在试验研究范围内，Fe3O4磁性液体润滑下的摩擦因数比油润滑低，MoDTC增强型磁性液体的摩擦因数低于Fe3O4磁性液体的摩擦因数，且MoDTC质量分数为6%时减摩效果较佳；当载荷在25~45 N范围内，MoDTC增强型磁性液体的摩擦因数先随载荷增大而减小，超过临界值30 N后，摩擦因数随载荷增大而增大。研究结果表明，磁性液体中加入适量的MoDTC具有较好的减摩性能，能在一定程度上改善磁性液体的润滑性能。     

油润滑下MoSi2材料的摩擦磨损性能

运用M-200型摩擦磨损试验机测定了油润滑条件下MoSi2与45调质钢、45淬火钢和CrWMn钢配对时的摩擦磨损性能，采用扫描电镜和微探针分析了摩擦副表面的形貌，探讨了磨损机理：结果表明：采用20号机械油润滑可有效地降低MoSi2材料的磨损率及摩擦因数；与低硬度的45调质钢和45淬火钢对摩时，MoSi2材料的主要磨损机制为晶间断裂、疲劳断裂、轻微粘着磨损和磨粒磨损；MoSi2材料与高硬度的CrWMn钢对摩时，主要磨损机制表现为粘着磨损、微犁削式磨粒磨损，并在偶件表面材料凸点的前端形成楔块。     

Dry friction and wear characteristics of nickel/carbon nanotube electroless composite deposits

Ni/carbon nanotube (Ni/CNTs) composite coatings were deposited on carbon steel plate by electroless deposition. The friction and wear properties were examined under dry sliding conditions using the ball-on-disk configuration. For reference, carbon steel plate was coated with Ni, Ni/SiC and Ni/graphite. The results show that the Ni/CNT coating has a microhardness value of 865 Hv, greater than for SiC reinforced composite deposits. The Ni/CNTs composite coating possesses not only a higher wear resistance but also a lower friction coefficient, resulting from their improved mechanical characteristics and the unique topological structure of the hollow nanotubes.     

Tribological behaviour of carbon and low alloy steels: effect of mechanical properties and test conditions

Abstract

In this paper, the effects of mechanical properties and test conditions on the tribological behaviour of ISO C45 carbon steel and ISO 42CrMo4 low alloy steel were studied. The tribological tests were carried out, without lubrication, on a reciprocating friction tester. Cylinder on flat contact configuration was adopted. The results showed that there is no obvious relationship between the mechanical properties and the friction ones. However, the variation in the coefficient of friction depends on the test conditions. In contrary to normal load, the effect of sliding speed on the coefficient of friction is not the same for the two steel nuances. The tribological properties are dependent, however, on the nature of wear debris.     

精密下料中圆形锤头棒料摩擦副的摩擦学性能分析

针对精密下料中存在的圆形锤头棒料摩擦副磨损严重问题，借助WTM-2E型可控气氛摩擦磨损试验仪，研究了不同转速和不同质量分数纳米MoS2添加剂下的GCr15钢块45钢柱摩擦副的摩擦磨损性能。结果表明：随着上摩擦副(45钢柱)的转速增加，磨损行程变长，摩擦因数和磨损量呈减小趋势，磨损表面形态由黏着磨损转变为磨粒磨损。采用声发射技术对摩擦副表面磨损状态进行实时监测，定量确定出质量分数为0.5%的纳米MoS2添加剂的减摩抗磨效果最佳。