多孔UHMWPE的制备与摩擦学性能研究

用热压成型法制备多孔超高分子量聚乙烯(UHMWPE)和普通UHMWPE试样,在改制的摩擦磨损试验机上考察2种试样在水润滑和牛血清润滑下的摩擦磨损性能。结果表明:普通UHMWPE均处于边界润滑区域;多孔UH-MWPE在较低载荷下因可以获得额外的润滑而形成混合润滑,摩擦因数和磨损量较低,其磨损机制为轻微的擦伤磨损;随着载荷的增加,多孔UHMWPE试样的磨损量明显上升并高于同等条件下普通UHMWPE,呈现较严重的切削磨损;多孔UHMWPE只适合应用于低载工况下。     

水润滑条件下高岭土填充UHMWPE基复合材料的摩擦学特性

分别用釜内聚合和机械混合两种方法制备高岭土填充UHMWPE基复合材料,对其在水润滑条件下的滑动摩擦磨损特性进行了试验研究,并通过对磨损表面形貌的观察分析,对材料的磨损机理进行了探讨.结果发现,水润滑对UHMWPE/Kaolin?5钢摩擦副的减磨(摩)作用显著;填充适量高岭土可以明显提高UHMWPE在水润滑条件下的摩擦磨损性能;釜内聚合方法制备的UHMWPE/Kaolin的磨损率相对较低,具有广阔的应用前景.     

几种水润滑轴承摩擦学性能的研究

利用摩擦试验机对3种水润滑轴承材料进行摩擦研究,对比水润滑下不同载荷和转速的摩擦因数。并通过干摩擦实验对水润滑轴承材料进行考核,对水润滑轴承材料的断水安全性能进行评价。结果表明:3种水润滑轴承材料的摩擦特性均为典型的Stribeck曲线,在高载荷下均具有较好的性能,摩擦因数相差不大。国产水润滑轴承材料具有良好的干摩擦性能。国产水润滑轴承材料在摩擦性能方面已经达到甚至超越了国外同类产品。     

UHMWPE基水润滑轴承摩擦及润滑特性的试验研究

针对纤维填料改性UHMWPE水润滑轴承的摩擦磨损性能进行研究。在平面摩擦磨损试验机上对玻璃纤维及碳纤维填料对UHMWPE复合材料摩擦性能进行试验,并分析GF-CF-UHMWPE材料与Thordon SXL材料在干摩擦、水润滑工况下的摩擦因数及磨损量。最后,采用径向水润滑轴承试验台对比研究了GF-CF-UHMWPE轴承和Thordon SXL轴承在不同载荷下摩擦因数随转速的变化规律。结果表明:纤维填料能显著增强UHMWPE的减摩性和耐磨性,GF-CF-UHMWPE材料具有更好的耐温性能,线性热膨胀系数也显著减小;GF-CF-UHMWPE轴承具有相同载荷下启动转速低,启动摩擦因数小的特性。     

一种新型摩擦材料在水润滑下的摩擦学性能研究

采用环块式摩擦磨损实验研究了一种新型摩擦材料在水润滑状态下不同载荷与转速对试样摩擦学性能的影响,并对比干摩擦条件下的摩擦学性能变化,借助磨损表面形貌观察分析其磨损机理。实验结果表明:水润滑条件下,摩擦系数随着载荷的增大而减小,随着转速的提高先增加后减小;磨损率随着载荷与转速的提高都减小。相同载荷与转速下,干摩擦时磨损机理以磨粒磨损和黏着磨损为主,而水润滑条件下水形成边界润滑,磨损机理以磨粒磨损和轻微的黏着磨损为主;水润滑条件下摩擦系数和磨损率均低于干摩擦,主要是由于水起到了润滑和冷却的作用,阻止了转移膜的形成,并在材料表面形成水膜起到了边界润滑的作用。     

润滑点接触粗糙表面滑动摩擦因数的实验研究

利用多功能微摩擦试验机,在轻载荷条件下测量了具有横向纹理圆盘表面的摩擦因数,得到了包括流体润滑、混合润滑和边界润滑完整的Stribeck曲线。考虑了载荷和时间对实验结果的影响,对不同粗糙度表面的Stribeck曲线进行了比较。实验的初步结果表明:增加载荷与实验时间,会获得更加稳定的实验结果;表面越粗糙,从混合润滑向流体润滑转换的临界速度越大;表面越光滑,Stribeck曲线的“谷底”越明显。     

不同水润滑尾轴承材料摩擦磨损性能比较

水润滑尾轴承材料对其摩擦磨损性能有着较大影响,为合理选取制作轴承的材料,选择3种目前业界较为常用的水润滑轴承材料:超高分子量聚乙烯(UHMWPE)、聚四氟乙烯(PTFE)、丁腈橡胶(NBR),使用CBZ-1船舶轴系摩擦磨损试验机对其在2种常见摩擦速度、不同程度比压下的摩擦磨损性能进行研究,并通过表面形貌分析比较其磨损机制。结果表明:低转速工况下UHMWPE与PTFE的水润滑性能近似,略高于NBR;高转速工况下UHMWPE的水润滑性能高于PTFE和NBR,但NBR的工作稳定性优于UHMWPE和PTFE。     

UHMWPE与橡胶共混水润滑轴承摩擦磨损性能试验研究

为改善丁腈橡胶水润滑轴承的摩擦学性能，以丁腈橡胶为基体，通过添加不同量的超高分子量聚乙烯（UHMWPE）粉末（分别为丁腈橡胶量的12%、50%、100%）制得3种复合材料；分析不同复合材料的结构，研究其在水润滑条件下的摩擦磨损特性，并与纯丁腈橡胶和纯UHMWPE材料进行对比。结果表明：制备的UHMWPE与丁腈橡胶复合材料中，UHMWPE以分散相的形式分布在丁腈橡胶基体中，分布较为均匀；UHMWPE的加入提高了丁腈橡胶材料的自润滑性能，其中UHMWPE的添加量为丁腈橡胶的50%和100%时复合材料在低速时的摩擦因数明显减小；UHMWPE的加入提高了丁腈橡胶基体的硬度，改善了复合材料摩擦表面的挤压变形，使得复合材料的磨损量有所降低。研究表明，一定添加量的UHMWPE添加量可明显改善丁腈橡胶水润滑轴承的摩擦学性能，其最佳添加量为丁腈橡胶的50%。     

水凝胶/热塑性聚氨酯复合材料在水润滑条件下的摩擦学性能

为提高水润滑轴承的承载能力，利用水凝胶在水润滑条件下的水合作用来改善热塑性聚氨酯（TPU）轴承材料的摩擦学性能。利用聚乙烯醇、海藻酸钠、壳聚糖等材料制备水凝胶颗粒，并通过熔融共混法制备水凝胶/TPU复合材料；在0.3和0.5 MPa的载荷下测试复合材料的摩擦磨损性能，利用激光干涉表面轮廓仪和扫描电子显微镜观察其磨损表面形貌，分析其磨损机制。结果表明：水凝胶微粒可以通过水合润滑改善摩擦副的润滑条件，从而降低摩擦因数和磨损量，提高复合材料的摩擦性能；水凝胶质量分数4%时复合材料具有最佳的摩擦磨损性能，其在0.3和0.5 MPa工况下相对于TPU试样的平均摩擦因数减少率分别为52.31%和43.94%。研究结果为开发高性能水润滑轴承材料提供了一种方法。     

凹坑织构对石墨材料水润滑性能的影响

为提高核主泵屏蔽电机用水润滑石墨轴承的摩擦润滑性能,采用高速雕铣机在石墨试样表面加工不同形状、深度和面积占有率的凹坑织构,通过水润滑条件下的销盘摩擦试验,测试分析凹坑织构结构参数对石墨材料水润滑性能的影响。结果表明：在水润滑条件下凹坑织构具有一定的减摩效果,随着转速的增加,凹坑织构的动压效应增强,石墨试样摩擦因数减小;随着载荷的增加,石墨试样摩擦因数减小;随着凹坑深径比、面积占有率的增加,石墨试样摩擦因数均呈现先减小后增大的变化趋势,当凹坑深径比为0.5、凹坑面积占有率为3%左右时,石墨试样摩擦因数最小;相较三角形凹坑织构,正方形凹坑和圆形凹坑织构的减摩效果更好。     

表面织构对水润滑轴承混合润滑性能的影响

为分析表面织构对水润滑轴承混合润滑性能的影响,基于平均Reynolds方程及JFO空化边界条件建立带有表面织构的水润滑轴承混合润滑模型并数值求解,获得不同织构参数下水润滑轴承的Stribeck曲线。研究结果表明:表面织构是否能改善润滑性能与其深径比及面密度参数密切相关,织构的引入并不一定能降低水润滑轴承的摩擦因数;表面织构的面密度和深径比存在最优值,能使水润滑轴承获得最大的膜厚比与最小的摩擦因数,并在较低的转速下由混合润滑状态进入流体动压润滑状态。     

界面滑移条件下点接触Stribeck曲线的实验研究

采用高黏度聚异丁烯润滑油,在光学弹流实验机上考察球-盘接触纯滑条件下的摩擦因数随卷吸速度和载荷的变化。结果表明,随着卷吸速度的增加,球-盘接触副进入弹流润滑并向流体动压润滑转变的过程中,摩擦因数并不像传统的Stribeck曲线一样,随着卷吸速度的增加而单调增加,而是呈现先上升、后下降、再上升的趋势,其中摩擦因数下降时的起始速度大致为凹陷出现的速度,摩擦因数再上升时的速度大致是润滑进入动压润滑的速度。初步论证界面滑移为产生上述波动的主要原因。     

UHMWPE复合材料水润滑轴承润滑状态转变性能研究

水润滑轴承润滑介质的黏度较低,轴承动压润滑难以形成。研究水润滑轴承润滑状态转变特性,可为水润滑复合材料轴承的设计和优化提供依据。建立水润滑轴承流固耦合计算模型,研究轴承承载力、水膜压力、轴承变形量随工况的变化关系,提出水膜厚度测试方法,研究轴承摩擦因数、水膜厚度随转速、负载的变化规律。研究结果表明:随偏心率和转速增大,轴承承载力、最大水膜压力和最大变形量均逐渐增大;随转速增大,轴承承载力、最大水膜压力和最大变形量的增幅逐渐减小。试验发现随着负载增大,改性UHMWPE轴承从混合润滑向动压润滑转变的膜厚比逐渐减小。     

Nanocomposite UHMWPE–CNT Polymer Coatings for Boundary Lubrication on Aluminium Substrates

The boundary lubrication regime plays a very important role in determining the life span of any of the two mating parts under liquid-lubricated conditions. It is during the start\stop cycles when insufficient fluid is available to fully separate the surfaces in relative motion and thus unusual wear takes place; a case of boundary lubrication. The aim of this work is to study the feasibility of using polymer coatings as boundary lubricants. This study investigates the friction and wear properties of ultra-high molecular weight polyethylene (UHMWPE) films coated on aluminium substrates under dry and base oil (without any additives)-lubricated conditions. In order to increase the load bearing capacity of the UHMWPE coatings, 0.1 wt% of single-walled carbon nanotubes are added. Experiments are carried out on a custom-built tribometer simulating a line contact between a polymer-coated cylindrical Al surface (shaft) and a flat uncoated Al plate as the counterface. The experimental parameters such as the normal load and the sliding speed are selected to simulate the boundary and mixed lubrication regimes for comparison purposes. Specific wear rates of the polymer films and bare Al surface under lubricated conditions are also calculated. Stribeck curves have been generated to evaluate the effectiveness of the pristine UHMWPE and the nanocomposite coatings in the various regimes of lubrication, especially the boundary lubrication regime. It is observed that the selected polymer coatings are effective in protecting the metallic surfaces without causing any observable oil contamination with wear debris.     

Tribological properties of AlCoCrFeNiCu high-entropy alloy in hydrogen peroxide solution and in oil lubricant

Pin-on-disc tests to investigate the tribological behavior of AlCoCrFeNiCu high-entropy alloy under lubrication conditions with 90% hydrogen peroxide solution and lubricant oil, respectively, were performed. The study demonstrates that the AlCoCrFeNiCu high-entropy alloy lubricated correspondingly with lubricant of 90% hydrogen peroxide solution (hereafter termed hydrogen peroxide lubricant) and lubricant oil significantly improves its friction and wear-resistance properties. Results showed that the friction coefficient, after a grinding stage, of the rubbing pair was lower than that with normal lubricant oil. The AlCoCrFeNiCu alloy in the lubricant with 90% hydrogen peroxide solution and lubricant oil exhibits a high resistance to wear. Analysis of the worn surface revealed that the AlCoCrFeNiCu high-entropy alloy lubricated with the hydrogen peroxide lubricant exhibited signs of inhomogeneous polishing oxidation and abrasive wear, with the wear mechanism changing with sliding distance, while the rubbing pair in normal lubricant oil is mainly dominated by abrasive wear.     

The Effect of FeS Solid Lubricant on the Tribological Properties of Bearing Steel under Grease Lubrication

In order to improve the tribological properties of 52100 steel under grease lubrication, FeS solid lubricant was used in two ways. Low-temperature ion-sulfurization technology was utilized to prepare solid lubricant iron sulfide (FeS) films on the surface of 52100 steel, and FeS particles were mixed into the lithium grease as additive. The friction and wear properties were examined systematically on a “ball-on-disc” testing machine. The results showed that the tribological properties of bearing steel under grease lubrication can be improved either by using ion-sulfurization technique or by adding FeS microparticles into the grease. The tribological performance of sulfurized surface lubricated by grease is better than that of a plain surface lubricated by grease containing FeS microparticles at lower load and speed. The plain surface lubricated by the grease containing FeS micropaticles possesses better antiwear property under harsher conditions. The mechanism of the experimental results is discussed in detail.     

Tribological behaviours of PA/UHMWPE blend under dry and lubricating condition

Dry-sliding and lubricated friction and wear behaviours of polyamide (PA) and ultra-high molecular weight polyethylene (UHMWPE) blend were studied using a pin-on-disc method (polymer pin sliding against a stainless steel disc) at room environment. The tribological performance of PA and UHMWPE were also investigated for the purpose of comparison. The worn surfaces were examined using a scanning electron microscope (SEM) and optical microscope. It was observed that PA specimen demonstrated highest friction coefficient, UHMWPE the lowest in both dry-sliding and lubricated sliding test. The friction of PA could be sufficiently decreased by blending with UHMWPE. Statistical analysis suggested the relationship between the wear volume loss and the sliding distance could be expressed by a linear model for dry-sliding, while a logarithmic model was determined for lubricated sliding. The difference in wear modes between both sliding series suggested that there was change in the mode of material removal process. The lower wear rate in lubricated sliding was attributed to the elastohydrodynamic or partial elastohydrodynamic lubrication through the development of a continuous lubricant film between the polymer and the counterface, while the high wear rate of the specimens, in dry-sliding test, was mainly caused by fatigue process due to the repeated action of tearing and crack-propagation.     

The Critical Condition for the Transition from HL to ML in Water-Lubricated SiC

Silicon carbide (SiC) with water lubrication is being considered as the most promising combination to replace metals and oil for sliding bearings and mechanical seals of machines working in water. The basic properties of the Stribeck curves of water lubricated SiC in parallel contact, especially, the critical conditions for the transition from HL to ML were studied experimentally. The hydrodynamic lubrication regions and minimum friction coefficients of metal pair in oil and SiC pair in water are compared to give a quantitative value of the oil viscosity range, in which metal/oil can be directly replaced by SiC/water for triboelements.In order to improve the load-carrying capacity of SiC sliding bearings for the increasing strict demands from industry, a surface texture was introduced to one of the contact surfaces by means of reactive-ion etching. The effect of surface texture on the lubrication regimes and the minimum friction coefficient were evaluated experimentally.