基础油对锂基润滑脂流变性的影响

为考察基础油对锂基润滑脂流变性的影响,在稳态剪切流和小幅振荡剪切流下研究不同黏度基础油制备的锂基润滑脂的流变参数。通过分析触变性、屈服应力,表观黏度、储存模量和应变幅度等流变参数,探讨基础油黏度对流变性的影响。结果表明:基础油的黏度越小,锂基润滑脂的黏弹性表现更加显著,破坏其结构所需要的能量越大,其结构更加稳定。     

增黏剂对锂基润滑脂流变性能的影响

制备含有不同种类增黏剂的锂基润滑脂,测试润滑脂的锥入度和相似黏度;采用流变仪通过剪率控制下的稳态流变试验和应变控制下的动态流变试验,研究增黏剂种类对锂基润滑脂流变性的影响。结果发现,加入增黏剂后,锂基脂的弹性模量减小,形变增大,即弹性特征相对减弱,黏性特征相对增强,从而润滑脂更易变形,不易流动,产生的形变更易恢复;在本研究试验条件下,不同增黏剂对基础脂流变性的影响程度不同,聚甲基丙烯酸酯的影响最为显著,小分子量的乙丙共聚物的影响最小。     

滚动轴承润滑脂的噪声特性及低噪声脂的合成

通过研究锂基脂的组成及合成工艺对润滑脂的噪声影响、分析润滑脂的结构,掌握滚动轴承润滑脂的噪声特性,合成低噪声脂。分别采用轴承振动(速度)法和轴承振动(加速度)法对合成的脂进行噪声值测试,并对合成的锂基脂各项理化指标进行测试。采用扫描电镜,通过冷冻复型法分析润滑脂产生噪声的原因。发现以酯类油与环烷基矿物油的混合油做基础油时,合成的锂基脂具有较好的噪声特性。基础油为矿物油时,采用控温慢冷法合成的锂基脂具有较好的噪声特性;基础油为酯类油与矿物油的混合油时,采用自然冷却法合成的锂基脂具有较好的噪声特性。通过综合考察润滑脂结构、滚动轴承振动噪声值及各项理化指标值,确定降噪效果较好的润滑脂组成及制备工艺,合成一种低噪声滚动轴承锂基脂,并对该脂的轴承寿命进行测试。     

基于AR 2000ex型流变仪的润滑脂性能研究

不同基质的润滑脂由于其成分的差异,受到剪切后黏度的变化程度不同。利用AR2000ex型流变仪研究3种不同基质的润滑脂在不同工作阶段的流变性能。结果表明,通过控制剪切速率得到特定条件下的流变曲线,可以分析出润滑脂在性能上的差异;锂基润滑脂无论是停止工作时的稳定性,还是工作时受剪切情况下的润滑性能,都优于钙基润滑脂和尿素基润滑脂;润滑脂的流变曲线基本符合Herschel-Bulkley模型,而且润滑脂的触变性表现为影响润滑脂的屈服应力。     

润滑介质对织构化表面摩擦学性能影响的实验研究

采用纳秒激光烧蚀技术在铍青铜盘试样表面加工3种不同参数圆形微凹坑织构,选用石油装备中常用的低黏度L-CKD150润滑油和高黏度复合锂基润滑脂为润滑介质,开展不同润滑环境下销-盘摩擦学实验,对比分析L-CKD150润滑油和复合锂基润滑脂对织构表面摩擦磨损性能的影响差异。实验结果表明:2种不同润滑环境下,合理参数织构均可有效提高表面润滑性能、减少摩擦磨损;润滑介质对织构表面摩擦磨损性能的影响差异与接触压力有关,接触压力较低时,L-CKD150润滑油润滑性能优于复合锂基润滑脂,接触压力较高时则复合锂基润滑脂润滑性能更优;相同工况下,相比于L-CKD150润滑油润滑,复合锂基润滑脂润滑时最优织构直径更大。     

锂基润滑脂FE9寿命的影响因素探讨

介绍了滚动轴承润滑脂测试仪FE9的测试条件及测试润滑脂寿命的重要意义,并以锂基润滑脂为研究对象,探讨油分离度和极压抗磨性对润滑脂寿命的影响,试验结果表明:锂基润滑脂油分离度过大或过小都会影响润滑脂寿命,合理选择锂基润滑脂极压添加剂不仅可以提高润滑脂寿命,而且可以使轴承运转更平稳。     

一种耐轴承腐蚀和磨损的复合锂基润滑脂的研制

研究不同类型极压抗磨剂、抗氧剂和防锈剂等对复合锂基润滑脂性能的影响,并复配一种多功能复合添加剂制备出复合锂基润滑脂。所研制复合锂基润滑脂的梯姆肯值为266 N、高温下氧化诱导期为761 min、滴点大于330℃,且通过了FE 8轴承磨损和EMCOR轴承腐蚀台架的检测。研究结果表明:所研制的复合锂基脂具有优异的极压抗磨、高温抗氧及耐轴承腐蚀和磨损等性能,应用效果良好。     

导电复合锂基润滑脂润滑的制备及性能研究

以聚α烯烃(PAO)为基础油,以复合锂皂为稠化剂,并添加抗氧、极压和导电添加剂,制备一种导电复合锂基润滑脂,用高速往复摩擦磨损试验机和表面电阻测定仪测定其润滑性能和导电性能,并与国外商用润滑脂和国产导电润滑脂进行比较。通过光学显微镜观察磨斑表面发现,自制的复合锂基脂润滑的表面光滑平整,其润滑性能优于其他2种润滑脂;体积电阻测量结果表明,复合锂基脂的体积电阻率要远远小于国外商用润滑脂和国产导电脂,说明其导电性也要优于其他2种润滑脂。研究表明,选用的有机导电介质不但降低了体积电阻,而且形成的摩擦保护膜也提高了其润滑性能。     

极压锂基润滑脂的生产与应用

极压锂基润滑脂具有长寿命、多效能等特点,是现代润滑脂发展的方向。提高我国润滑脂的生产和使用水平,是我国研究和生产工作者的努力方向。我厂担负了为1700轧机提供极压锂基润滑脂的生产任务。几年来,在石油化工科学研究院和一机部广州机床研究所研制报告的基础上,我们对极压锂基润滑脂工业性生产的冷却、极压添加剂的选择及其产品的使用进行了一些探索,现介绍如下:     

均质化处理对锂基润滑脂微观结构和性能的影响

为探讨均质化对润滑脂稠化剂微观结构和性能影响,利用精密三辊研磨机以不同辊间距研磨锂基润滑脂,系统研究研磨前后锂基润滑脂的微观结构、锥入度、滴点、机械安定性、胶体安定性和流变学性能,并分析稠化剂微观结构与润滑脂性能的相关性.结果表明:与未研磨的润滑脂相比,研磨可提高锂基润滑脂稠化剂的分散均匀程度;研磨后润滑脂的锥入度显著...     

Impact of Water on the Rheology of Lubricating Greases

The operational life of bearings is often determined by the performance of the lubricating grease. The consistency of the grease prevents it from leaking out of the bearing and provides good sealing properties. The possible ingress of water into the bearing will have a considerable impact not only on this consistency but also on the lubricating ability of the grease. There are numerous applications where water ingress may occur, such as in the steel, food, pulp, and paper industries. Some greases are less sensitive to water than others. No specific guidelines are available to select the proper grease for bearings subjected to water ingress. The goal of the article is to contribute to the development of such guidelines for greases subjected to water ingress by studying the impact of water on grease rheology. Fully formulated, commercially available greases with the most common thickeners and base oils are used as model greases. It will be shown that water strongly influences rheological properties such as zero-shear viscosity, yield stress, and storage modulus. Calcium sulfonate greases were found to become stiffer after absorbing a considerable amount of water, leading to an increase in zero-shear viscosity and yield stress. However, lithium, lithium complex, and polyurea greases were found to soften, with appreciable changes in measured rheological properties.     

Thermorheological behaviour of a lithium lubricating grease

Thermal-induced changes in the viscous and viscoelastic responses of lubricating greases have been investigated through different rheological techniques in a temperature range of 0–175 °C. Small-amplitude oscillatory shear and viscous flow measurements were carried out on a model conventional lithium lubricating grease prepared by inducing the in situ saponification reaction between 12-hydroxystearic acid and hydrated lithium hydroxide. The linear viscoelasticity functions dramatically decrease above 110 °C, but not below this critical temperature, which determines the maximum recommended operating temperature in relation to its durability and resistance under working conditions. Two different regions, below and above this critical temperature, in the plateau modulus versus temperature plot have been detected. From this thermal dependence, a much larger thermal susceptibility of the lubricating grease at temperatures above 110 °C is apparent. The thermo-mechanical reversibility of this material has been studied by applying different combined stress–temperature protocols. Regarding the viscous flow, a minimum in the shear stress versus shear rate plots appeared at temperatures above 60 °C, more pronounced as temperature increases, resulting from material instabilities. The experimental results obtained have been explained on the basis of the thermo-mechanical degradation of the lubricating grease microstructure.     

Evaluation of Thermal and Rheological Properties of Lubricating Greases Modified with Recycled LDPE

The influence that recycled low-density polyethylene (LDPE) and lithium thickener concentrations exerts on the thermal and rheological properties of lithium lubricating greases was investigated using different rheological techniques in a temperature range of 25–175°C. In this way, different lubricating grease formulations were manufactured by modifying the concentration of lithium 12-hydroxystearate and content of recycled LDPE. These lubricating greases were rheologically characterized through small-amplitude oscillatory shear (SAOS) and viscous flow measurements. In addition, bomb oxidation tests (BOTs) and thermogravimetric (TGA) analysis were carried out. From the experimental results obtained, it can be deduced that modified lithium lubricating greases can be considered thermo-rheologically complex materials. Different behaviors of the viscoelastic modulus with temperature as a function of thickener and recycled LDPE concentration were found. Two types of viscous flow behavior were observed depending on the grease composition: A plateau region appeared in a wide range of shear rates and, in some cases, a minimum in the flow curve was more pronounced at high temperatures. The modified lubricating greases studied showed lower thermal and oxidation stability than unmodified lithium lubricating greases.     

An Investigation into Grease Behavior in Thermal EHL Circular Contacts

The behaviors of two lithium lubricating greases were investigated under EHL circular contact through measurements of traction coefficients on a self-made rig in which the contact was continuously fed with fresh grease. The average values of Erying shear stress and shear modulus of the two lithium greases were obtained from traction experimental data using this rig. Based on the Evans-Johnson model and thermal analysis, we calculated the values of shear stress and traction coefficients of the two greases. The results show that the calculated traction coefficients agree fairly well with the measured data.     

润滑脂流变特性与小模数齿轮运转性能相关性研究

采用HAAKE RS6000高级旋转流变仪测试7种润滑脂的屈服应力、弹性模量、黏弹性、触变性和剪切时变性,分析润滑脂流变性对小模数齿轮运转性能的影响。结果表明:润滑脂在齿轮间运转过程中,运转电流和降噪性能与润滑脂流变性具有相关性,受流变特性的影响;稠度接近条件下,基础油黏度最高的润滑脂有最高的电流和最低的噪声;稠化剂含量低的润滑脂对齿轮降噪有利,但是并非稠化剂含量越低越好,稠化剂很少时,其黏附性减弱,齿轮运转过程中,润滑脂不易粘附于齿轮而起到降噪减摩效果。     

改性复合磺酸钙基润滑脂的研究

高碱值复合磺酸钙基润滑脂综合性能优异,被称为全新理念的润滑脂,但容易产生硬化问题。对复合磺酸钙基润滑脂进行了改性处理,并且对其硬化机制作了初步分析。结果表明:改性后的复合磺酸钙基润滑脂综合了复合锂基脂、聚脲基脂和复合磺酸钙基脂的性能优势,不仅解决了硬化问题,且该润滑脂具有特殊的纤维结构,从而赋予其极高的滴点、良好的高温极压润滑性能和低的摩擦因数。     

The Preparation and Tribological Investigation of Ni–P Amorphous Alloy Nanoparticles

Amorphous Ni–P alloy nanoparticles were synthesized by chemical reduction of nickel acetate in water reacted with sodium hypophosphite under stirring. The nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Results of XRD and TEM showed that nanoparticles have an average diameter 100 nm. And XPS analysis indicated that part of the surface of Ni–P amorphous alloy nanoparticles was oxidized. The tribological properties of the prepared Ni–P nanoparticles as an additive in lithium grease were evaluated with a four-ball friction and wear tester. The worn surfaces of the lubricated GCr15 steel were analyzed by means of XPS and scanning electron microscopy (SEM). The lubricating mechanisms were discussed on the basis of XPS and SEM analyses of the worn steel surfaces. The results show that these nanoparticles as a grease additive can effectively enhance the friction-reduction and antiwear ability of lithium grease. Tribochemical reactions were involved for steel–steel frictional pair lubricated with the lithium grease containing amorphous Ni–P alloy nanoparticles, with the formation of a boundary lubricating and protecting film composed of additives of lithium grease and tribochemical reaction products (iron phosphate, iron oxides, nickel oxide, nickel, etc.) of the lubricants. This contributes to improve the tribological properties of the lithium grease.     

A study on tribological behaviours of ZDDP in polymer thickened lubricating greases

Zinc Dialkyl Dithiophosphate (ZDDP) is a well‐known multifunctional additive for soap based lubricating greases. Polymers are being studied for their performance as lubricating grease thickeners and rheology modifiers. In this work the tribological study of ZDDP was carried out in polypropylene (PP), maleated polypropylene (mPP) and linear low density polyethylene (PE) thickened lubricating greases. Performance of lithium grease was taken as a reference. The tribological properties were evaluated using a four ball tester for EP properties and Optimol SRV‐III machine for coefficient of friction. The mechanism of action of ZDDP in polymer greases was established through analysis of the worn surface of steel balls with scanning electron microscope (SEM) and energy dispersive x‐ray spectroscopy (EDAX). The results show that the performance of ZDDP depends on the thickener system. The antiwear and EP property exhibited by ZDDP varies from polymer to polymer. Poor performance was observed with PP type thickener whereas performance in PE and lithium grease was comparable. Copyright © 2015 John Wiley & Sons, Ltd.     

On a New Method to Determine the Yield Stress in Lubricating Grease

An experimental study using both a controlled stress and a controlled strain rheometer has been undertaken to characterize lubricating grease in shear, creep, stress relaxation, and oscillatory flow, with a main focus on determining the yield stress. The yield stress was examined using a cone–plate and parallel-plate system with smooth and rough surfaces. Clear discrepancies were observed in the yield stress values obtained using different techniques where oscillatory strain sweep measurements seem to be the best choice. This technique is less sensitive to wall slip, shows good reproducibility, and is relatively easy to perform. The method also shows that the yield stress is a function of the imposed frequency and therefore of the time domain. At lower values of shear—that is, in the linear viscoelastic regime—there is no structural breakdown and the rheology of the grease can be described by the Maxwell model where the stress and the strain are almost proportional to each other. Based on this observation, a novel method to determine the yield stress is proposed: “The yield stress can be determined from the point where this linearity no longer applies.” This method is compared to those that are commonly used. The yield stress was found to depend exponentially on temperature and linearly on frequency.     

二硫化钼锂基润滑脂的老化性能预测

对二硫化钼锂基润滑脂进行加速老化试验,获得其质量变化率与老化温度及老化时间的变化规律。运用阿累尼乌斯方程和性能变化的时温关系式,采用线性回归方法推导出以二硫化钼锂基润滑脂质量变化率为性能指标的时温等效关系式。运用该模型可以推算不同贮存温度及不同贮存时间下二硫化钼润滑脂的质量变化情况,实现其老化性能的预测与评估。