4种轴承钢在水基泥浆中摩擦学性能研究

在油气井钻井过程中,大量井下工具在水基泥浆特殊环境中工作。井下工具中轴承部件工作条件苛刻,往往容易损坏,从而导致整个系统的失效。研究选取GCr15、9Cr18、G20CrNiMo、Cr4Mo4V等常用轴承钢为研究对象,制成盘销试样,在FALEX摩擦磨损试验机上模拟井下特殊工况,研究不同载荷、不同速度下试样的摩擦因数、磨斑直径及磨损形式。结果表明:水基泥浆中,当转速一定时,随载荷的增大GCr15、G20CrNiMo、Cr4Mo4V的摩擦因数变化不大,9Cr18的摩擦因数随载荷的增大而增大。当载荷一定时,GCr15、G20CrNiMo、Cr4Mo4V的摩擦因数随着转速升高而略微降低,9Cr18的摩擦因数整体上随转速的增大而增大。GCr15、G20CrNiMo和Cr4Mo4V的磨损形式主要为腐蚀磨损和磨粒磨损,但GCr15的腐蚀更严重。高速重载条件下(40 N,100 r/min),9Cr18的磨损形式由磨粒磨损转变为黏着磨损。     

凹槽型织构对钻头滑动轴承表面摩擦学性能影响分析

基于雷诺方程建立表面织构化滑动轴承润滑理论模型,探究不同织构参数(分布角度、深度、面积比、偏斜角度、长度)对钻头滑动轴承承载力和摩擦因数的影响规律.在油膜收敛和最小油膜厚度附近区域布置织构,有利于增加轴承表面润滑性能,而织构布置在油膜发散处反而会减小轴承承载力,增大摩擦因数.织构的最佳织构深度与轴承的工况相关,不同偏心率条件下最优织构深度不同,轴承所承载的载荷越大,凹槽型织构化轴承的最佳织构深度越深;摩擦因数随织构面积比的增加先增大后减小,当面积比为18％时,摩擦因数最小.织构深度对织构偏斜角度的影响较小,轴承摩擦因数随偏斜角度的增加逐渐减小;织构长度为轴承宽度的1/2时,轴承润滑效果最佳.     

铝合金表面纳米Al2O3-40%TiO2复相陶瓷涂层力学与摩擦学性能

为提高铝合金零部件的耐磨性能,运用等离子喷涂技术在7005铝合金表面制备纳米Al2O3-40%TiO2(NAT40)复相陶瓷涂层,分析该涂层的微观结构,测试其主要力学性能,研究其在干摩擦和3.5%NaCl溶液中的摩擦行为与机制。结果表明:NAT40涂层的显微硬度为638.6 HV0.5,断裂韧度为13.3 MPa.m1/2,与基体的临界结合力达到80.35 N,均高于微米Al2O3-40%TiO2(MAT40)涂层。干摩擦时,随着载荷从3 N增大至12 N,NAT40涂层的摩擦因数从0.20上升至0.32,其磨损失重也从1.3 mg增大到2.2 mg;轻载3 N时,涂层以微观切削磨损为主,而在重载12 N条件下,磨损表面闪温计算值达到541.65℃,导致涂层的强度和硬度下降,磨损机理变为多次塑变磨损、粘着磨损和氧化磨损。在3.5%NaCl溶液摩擦环境中,NAT40涂层在相同载荷条件下的摩擦因数较干摩擦时显著降低,但重载(12 N)时,其磨损失重却比干摩擦时增加22.7%;随着载荷的增加,涂层的磨损机理由疲劳磨损转变为应力腐蚀磨损。     

硬度对螺旋槽水润滑橡胶推力轴承摩擦磨损性能影响的实验研究*

水润滑橡胶推力轴承是船舶推进系统中提供轴向支撑力的重要零部件,其摩擦磨损特性严重影响船舶推进工作性能。开展螺旋槽水润滑橡胶推力轴承实验,测试2种橡胶硬度推力轴承在不同工况下的摩擦力,以及高速重载工况下实验前后橡胶层的表面形貌,分析转速、载荷、旋转方向、橡胶层硬度对摩擦因数的影响,以及推力轴承的主要磨损形式。结果表明:相同载荷下,随着转速的增加,2种硬度推力轴承的摩擦因数呈显著下降趋势,摩擦因数下降幅值最大达到了0.51;在高速时,载荷对摩擦因数的影响不显著;高硬度推力轴承在低速时摩擦性能表现更优,而低硬度推力轴承在高速重载条件下不易发生黏着磨损,因此,建议在低速重载条件下使用高硬度橡胶推力轴承,而高速重载条件下使用较低硬度的推力轴承。     

钻井液污染润滑脂对牙轮钻头轴承摩擦学性能的影响

高温或冲击载荷会引起钻井液泄漏进入复合锂基润滑脂,从而影响牙轮钻头滑动轴承润滑及摩擦磨损性能。采用MCR102旋转流变仪对含有不同质量分数钻井液的复合锂基润滑脂进行流变性测试,并采用MDW-1型摩擦磨损试验机开展牙轮钻头滑动轴承模拟工况下轴承单元摩擦学实验,研究钻井液质量分数对轴承摩擦磨损性能的影响。结果表明:钻井液的污染将降低润滑脂的黏度,改变润滑脂的流变性能;钻井液的污染总体上增大了滑动轴承单元摩擦因数及摩擦因数波动幅度,同时加大轴承的磨损,且在高转速下,润滑脂中较低含量的钻井液就会使滑动轴承单元的摩擦磨损达到最大值;钻井液中的超细碳酸钙和重晶石颗粒引起的磨粒磨损和犁沟效应,可能导致滑动轴承快速失效。     

不同涂层在甘油环境下的摩擦学性能对比研究

为提高甘油环境下摩擦副的抗磨能力,采用磁控溅射技术在单晶硅P(111)、316L不锈钢上分别制备DLC、CrN、TiN涂层。分别在大气及甘油环境下,利用多功能摩擦磨损试验机对涂层摩擦磨损性能进行对比研究,分析摩擦因数、磨损率及磨痕形貌的变化规律,并对比分析甘油环境中不同涂层与涂层配副在重载高速下摩擦力矩变化规律。结果表明:DLC涂层在大气环境下具有最优的减摩抗磨性能,DLC涂层和CrN涂层在甘油环境下均具有优良的减摩耐磨性能;在100 N载荷下DLC-CrN涂层配副在甘油环境下在整个测试过程中摩擦力矩比较小,且样块表面均无明显的磨损及划痕,表明DLC-CrN涂层配副在甘油环境及重载高速工况下具有优异的摩擦学性能。     

H62-UHMWPE自润滑材料的有限元设计及性能验证

利用有限元法对H62-UHMWPE自润滑材料进行结构设计,并对该材料进行了承载能力及摩擦磨损试验,结果表明,这种自润滑材料的承载能力为59.6 MPa,摩擦因数随转速的升高而增大,随载荷的增大而降低,当载荷为40 MPa,转速为50 r/min时,摩擦因数低于0.12,具有良好的耐磨性,低速条件下其磨损机理主要为轻微的粘着磨损,适合用于制造低速工况使用的自润滑轴承。     

大滑滚比工况下弹流摩擦试验研究

针对大滑滚比工况,在自行改造的双盘摩擦磨损试验机上,完成了一系列线接触弹流摩擦试验;测量了不同工况下的摩擦因数,对试验结果进行了全面的分析,得到了一系列摩擦曲线,反映了多种具体工况下,各工况参数对摩擦因数的影响.结果表明:载荷比较小时,摩擦因数对载荷或转速的变化非常敏感;随着载荷的增大,摩擦因数对载荷与转速的敏感程度急剧下降;大滑滚比工况下,摩擦因数随滑滚比的变化幅度不大;摩擦因数随载荷增大而减小,且减小幅度随载荷增大而减小;摩擦因数随转速增大而减小,且减小幅度随转速增大而减小.     

大滑滚比工况下弹流摩擦试验研究

针对大滑滚比工况,在自行改造的双盘摩擦磨损试验机上,完成了一系列线接触弹流摩擦试验;测量了不同工况下的摩擦因数,对试验结果进行了全面的分析,得到了一系列摩擦曲线,反映了多种具体工况下,各工况参数对摩擦因数的影响。结果表明：载荷比较小时,摩擦因数对载荷或转速的变化非常敏感;随着载荷的增大,摩擦因数对载荷与转速的敏感程度急剧下降;大滑滚比工况下,摩擦因数随滑滚比的变化幅度不大;摩擦因数随载荷增大而减小,且减小幅度随载荷增大而减小;摩擦因数随转速增大而减小,且减小幅度随转速增大而减小。     

轴受载变形产生的轴颈倾斜对滑动轴承润滑影响的研究

针对轴-轴承系统,建立了轴受旋转载荷作用时变形导致的轴颈倾斜对滑动轴承润滑性能影响的分析方法,并在研制的滑动轴承试验装置上进行了专项验证试验。试验结果表明,提出的基本方程、公式和分析方法可以满足研究要求。计算了轴受载变形导致轴颈倾斜情况下,轴承的油膜压力、端泄流量和轴颈摩擦因数等。结果显示,轴颈倾斜时,轴承油膜压力分布和油膜厚度分布有明显变化,最大油膜压力明显增加,最小油膜厚度减小很多,端泄流量略有增加,轴颈摩擦因数变化不大。     

Influence of different surface modification technologies on friction of conformal tribopair in mixed and boundary lubrication regimes

Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, and temperature. The overall frictional losses in machines are dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a sliding bearing/roller tribopair both in boundary and mixed lubrication regimes. A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range to enable studies in boundary and mixed lubrication regimes. The influence of application of different surface modification technologies on both the sliding bearing and the roller surfaces on friction has been studied. The rollers used in these studies were provided with five different coatings (hard DLCs and a soft self-lubricating coating). Additionally, two uncoated rollers having different surface roughness were also studied. Uncoated bearings were used in all tribopairs except two. These two bearings were coated with DLC and phosphate coatings respectively and uncoated rollers were the mating counterparts. Friction measurements were made on the new as well as the previously run-in surfaces. It was found that the rollers with self-lubricating coating resulted in lowest boundary friction closely followed by the rollers with the hardest DLC coatings. The DLC coating applied on to the bearing showed lower boundary friction after running-in. Mixed friction has been found to be mainly dependent on the surface topography characteristics of both the original and the run-in surfaces of bearings and rollers. The harder DLC coatings and the phosphated bearing showed the lowest mixed friction due to an efficient running-in of the bearing surface.     

Performance and Durability of High Temperature Foil Air Bearings for Oil-Free Turbomachinery

The performance and durability of advanced, high temperature foil air bearings are evaluated under a wide range (10 to 50 kPa) of loads at temperatures from 25° to 650 °C. The bearings are made from uncoated nickel based superalloy foils. The foil surface experiences sliding contact with the shaft during initial start/stop operation. To reduce friction and wear, the solid lubricant coating, PS304, is applied to the shaft by plasma spraying. PS304 is a NiCr based Cr₂O₃ coating with silver and barium fluoride/calcium fluoride solid lubricant additions.

The results show that the bearings provide lives well in excess of 30,000 cycles under all of the conditions tested. Several bearings exhibited lives in excess of 100,000 cycles. Wear is a linear function of the bearing load. The excellent performance measured in this study suggests that these bearings and the PS304 coating are well suited for advanced high temperature, oil-free turbomachinery applications.     

Comparison of tribological characteristics between aluminum alloys and polytetrafluoroethylene composites journal bearings under mineral oil lubrication

This study examined the tribological behavior of journal bearings made from polytetrafluoroethylene (PTFE) composites and aluminum (Al) alloys. The PTFE composite journal bearings consisted of a steel backing with a thickness of 1.6 mm, a middle layer of sintered porous bronze with a thickness of 0.24～0.27 mm, and a surface layer of PTFE filled with fluorinated ethylene propylene (FEP) powder and carbon fibers with a thickness 0.06～0.14 mm. The other was an aluminum alloy journal bearing consisted of a steel backing with a thickness of 1.5 mm and a surface layer of an Al-6Sn-6Si alloy with a thickness 0.35～0.75 mm. A series of lubrication tests were performed using a journal bearing tester under various normal loads. The tribological properties for each journal bearing were evaluated by measuring the lubricant oil temperature and friction coefficient as a function of the applied normal load. In addition, the chemical compositions and microstructures of the journal bearing materials used in this study was analyzed by inductively coupled plasma (ICP), optical microscopy (OM), and scanning electron microscopy (SEM), respectively. The experimental results showed that the Al alloy journal bearings reduce the friction coefficient by 28 % compared to the PTFE composites bearings. In addition, the Al alloy journal bearing worked properly at the maximum load of ～ 8,000 N without adhesion. However, the PTFE composite journal bearings exhibited strong adhesion at the loads ranging from 6300 to 8000 N. This suggests that the Al alloy is a more promising material in journal bearings than PTFE composites.     

沙尘环境对金属抗磨损特性的影响

通过向摩擦副所在隔离空间内鼓沙的方式实现对自然沙尘环境的模拟。在沙尘环境和干摩擦情况下,对比研究了随着载荷的增加,沙尘环境的存在对C52100铜、2124铝、AISI-1045钢、Z25铸铁、AISI-52100钢5种不同硬度的典型金属抗磨损行为的影响。结果表明,在沙尘条件下,5种金属的磨损率随载荷的变化呈现一定的变化规律,C52100铜和52100钢的磨损率均随载荷的增加而减小,2124铝和Z25铸铁的磨损率随载荷的增加而增大,而1045钢的磨损率则先增大后减小,但磨损率随载荷变化非常小。沙尘的存在使52100钢、1045钢和Z25铸铁的磨损率比干摩擦条件下有大幅度的减小,但是却加剧了2124铝在较高载荷下的磨损,这说明对不同的材料而言,沙尘所起的作用是不同的,它可能会加剧材料的磨损,但也有可能提高材料的抗磨损性能。     

Wear properties of DLC-coated steel rollers running with highly contaminated lubrication

The presence of hard contaminants in lubrication can lead to the premature failure of rolling bearings. To reduce the negative effect of such contaminants, hard carbon-based coatings (diamond-like carbon; DLC) can be applied to the surfaces of steel bearings. DLC coatings generate a low friction and a high sliding wear resistance to enhance the tribological properties and improve the durability of running components. This work explores the merits of DLC coatings for use in very demanding applications, such as in highly contaminated environments. The wear properties of DLC-coated bearing rollers were evaluated by comparing them with uncoated rollers. The degree of wear found on the coated rollers was serious, especially under relatively high contaminant concentrations. The three-body abrasive wear produced a relatively coarse scoring of the coating surface, which caused the corresponding disc to suffer more damage than the disc running against an uncoated roller under the same operating conditions. The results indicate that supposedly wear-protective coatings cause even more damage to running surfaces once they have been broken up by hard contaminants, and highlight the importance of keeping the bearing coating intact. In practise, it is important to eliminate contaminants from the lubricant of rolling bearings, in particular for bearings with a DLC anti-wear coating.     

Super low friction of DLC applied to engine cam follower lubricated with ester-containing oil

This paper presents a material combination that reduces the friction coefficient markedly to a superlow friction regime (below 0.01) under boundary lubrication. A state approaching superlubricity was obtained by sliding hardened steel pins on a hydrogen-free diamond-like carbon (DLC) film (ta-C) lubricated with a poly-alpha-olefin (PAO) oil containing 1 mass% of an ester additive. This ta-C/steel material combination showed a superlow friction coefficient of 0.006 at a sliding speed of 0.1 m/s. A hydrogencontaining DLC coating/steel combination also showed a lower friction coefficient in air than a steel/steel combination, 0.1 vs. 0.8, but no large reduction was observed when the sliding surfaces were lubricated with ordinary 5W-30 engine oil and the PAO oil containing an ester additive. The friction coefficient of the hydrogen containing DLC/steel combination lubricated with the PAO containing an ester additive was above 0.05. On the other hand, the superlow friction performance demonstrates that the rolling contact friction level of needle roller bearings can be obtained in sliding contact under a boundary lubrication condition. It is planned to apply this advanced DLC coating technology to valve lifters lubricated with a newly formulated engine oil in actual mass-produced gasoline engines. A larger friction reduction of more than 45% is expected to be obtained at an engine speed of 2000 rpm.     

Tribological Dependence of the High-Performance Ferrous-Based Coating on Different Coating Counterparts in Engine Oil

A ferrous-based coating with significant chromium was fabricated on aluminum alloy substrate using a plasma spray technique. The tribological performance of the as-fabricated ferrous-based coating sliding against different coatings including Cr, CrN, TiN, and diamond-like carbon (DLC) in an engine oil environment were comparatively studied. Results showed that the high hardness of the sprayed ferrous-based coating was achieved due to the dispersion strengthening effect of Cr₇C₃ phase embedded in the austenite matrix. The ferrous-based coating exhibited low friction coefficients when coupled with these four coating counterparts, which could be attributed to the boundary lubricating effect of engine oil. However, both friction and wear of the ferrous-based coating were different when sliding against these different coating counterparts, which might be closely related to the surface roughness, self-lubricating effect, and mechanical properties of the coupled coatings. Ferrous-based coating sliding against CrN and DLC coatings exhibited good tribological performance in engine oil. The best coating counterpart for the ferrous-based coating in an engine was DLC coating.     

高速板带轧机四列滚动轴承非均匀接触力学性能及修形优化研究

针对高速板带轧机四列滚子轴承在偏载运行下滚子-滚道非均匀接触力学性能及滚子修形优化进行研究。建立了滚子-滚道接触力学模型,模拟了其偏载运行下的接触力学性能。提出滚子接触应力均匀分布原则,采用非对称对数曲线对四列滚子母线修形优化。研究表明：偏载轧制导致四列滚子承载分布严重不均,以某冷轧机四列滚子轴承为例,载荷分布偏差较常规轧制增加20%,列间接触应力差接近200MPa,单列滚子轴线方向接触应力差接近60MPa。接触应力差随修形量k₃差值减小而减小,当k₃差值减小到一定程度时,接触应力差反而变大,最终修形曲线优化参数为k₁=1.3,k₂=1,k₃=0.014-0.011。研究为延长轴承使用寿命、保证轧机安全稳定运行提供理论依据,具有重要工程意义。     

The effect of substrate properties on tribological behaviour of composite DLC coatings

The unique features of DLC coatings in providing low friction and low wear and, at the same time, causing low wear to the counterface make them very attractive in industrial applications, in improving tribological performance of mechanical components on various substrates. In this study, composite DLC coatings have been deposited on sintered ferrous alloy, M42 tool steel, 2618 aluminium alloy, and 6063 aluminium extrusion substrates using the combined CFUBMS–PACVD technique. The effect of mechanical properties of substrate materials on tribological behaviour of the composite DLC coatings has been investigated at various loads on a ball-on-disk wear machine in dry air. A transition load was usually observed for coatings on the various substrates except for the aluminium extrusion; above the transition load the coating was completely destroyed via some spallation/fragmentation process after 2 h sliding, and the wear rate increased dramatically with further increase in load. The coating system on sintered ferrous alloy substrate exhibited the highest transition load among the four types of substrates studied. This is considered to have resulted from the combined effects of the lower elastic modulus of the porous sintered ferrous alloy substrate, which decreases the stress concentrations in the contact region, and the surface roughness and porosity, which enhance the bonding strength between the coating and the substrate under multi-contact conditions. The high elastic modulus of the tool steel substrate leads to tensile stress conditions in the sliding contact region and therefore makes coatings deposited on such a substrate more prone to breakdown/fragmentation, resulting in a transition load close to that for coatings on the soft 2618 aluminium alloy substrate. For coatings on the 6063 aluminium extrusion substrate, significant plastic deformation occurred in the substrate at loads above 1.5 N. However, despite the heavy deformation in the substrate, coatings on this substrate were not scraped off, as were coatings on the 2618 aluminium alloy substrate, even at a load as high as 20 N. The specific wear rate increased continuously with load, no apparent transition load being explicitly identifiable. This study shows that hard DLC coatings can be applied on both hard and soft substrates for improvement of the tribological behaviour of mechanical components.     

Effect of Normal Load and Sliding Distance on the Wear Behavior of NiTi Alloy

Effect of normal load and sliding distance on the room temperature dry sliding wear behavior of a Ti-50.3 at% Ni alloy against a bearing steel was studied. The wear tests were conducted using a pin-on-disk tribometer under normal loads of 20, 40, 50, 60 and 80 N for sliding distances up to 1000 m. The wear results showed that the wear rate of NiTi alloy decreased as the normal load increased from 40 N to 60 N. Formation of iron rich tribological oxide layers under the higher loads could be the main reason of decrease in the wear of NiTi alloy. Increasing the sliding distance decreased the wear rate of NiTi alloy under normal loads of 60 N and 80 N, which was attributed to the formation of more stable iron rich tribological oxide layers on the worn surfaces of NiTi alloy.