Tribological studies of 1-alkyl-2,5-dithiohydrazodicarbonamides and their Mo–S complexes as EP and multifunctional additives

This communication reports a comparative study of the anti-wear, extreme pressure and friction reducing properties of 0.5% (w/v) admixtures of paraffin oil with 1-alkyl-2,5- dithiohydrazodicarbonamide ligands and their Mo–S complexes, i.e. μ-hydroxo-μ-(1-alkyl-2,5-dithiohydrazodicarbonamido)-bis-[dioxohydroxo molybdenum VI] using 12.7 mm diameter steel bearing balls in a four-ball test. In particular, the additive μ-hydroxo-μ-(1-n-butyl-2,5-dithiohydrazodicarbonamido)-bis-[dioxohydroxo molybdenum VI] exhibits an increase in the load carrying capacity of the lubricant and a decrease in the values of wear and coefficient of friction. The surface analysis of the wear-scar matrix of the used ball specimen has been investigated by SEM and AES techniques.     

Tribological studies of some N,S, and Cl containing extreme pressure additives

The antiwear and EP properties of certain p-chlorophenyl groups containing nitrogen and sulphur open-chain and cyclic compounds, in paraffin oil, were evaluated in a four-ball test. The performance of the additives were compared with a commercially available sulphur-phosphorus reference additive. All the additives, in general, exhibited good EP activity at different loads as compared to paraffin oil and the reference additive. However, the cyclic additives, e.g., 2-phenyl-3-phenylimino-5-p-Cl-phenylamino-1,2,4-thiadiazolidine, and 2-amino-5-p-Cl-phenylamino-1,3,4-thiadiazole, were found to possess good antiwear and EP properties in comparison to the plain paraffin oil, reference additive, and open chain additives. The wear surface tribochemistry and topography were studied using Scanning Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM) techniques, respectively. A comparative EP activity evaluation of 1-p-Cl-phenyl-2,5-dithiohydrazodicarbonamide and 3-p-Cl-phenylimino-5-(N-methylphenyl)amino-1,2,4-dithiazoline on steel bearing balls of different composition was undertaken to assess the suitability of replacing chromium alloy steel balls with cheaper carbon steel balls. The additive, 3-p-Cl-phenylimino-5-(N-methylphenyl)amino-1,2,4-dithiazoline exhibited its effectiveness on the alloy steel as well as low carbon steel bearing balls. A plausible explanation for the enhanced activity of additives is suggested and efforts made to correlate the effect of substituents and structure on the efficiency.     

Wear reduction using some extreme pressure lubricant additives and their tribological studies

Certain S-containing organic compounds were synthesized and their extreme pressure (EP) properties assessed. The series of compounds studied were: S-alkylisodithiobiurets, alkyl-S-alkyl xanthates, S-alkylisothioamides, S-benzylisothiocarbamides and 1-formamidino-2-benzyliso-3-arylthiocarbamides. These additives were compared with a commercial additive. The tribological end effects were studied using a Scanning Electron Microscope. Some of the compounds tested were found to be effective EP additives. Wherever possible, a plausible explanation for the enhanced activity has been given, and we have attempted to correlate the effect of substituents on efficiency. Also, the effect of additives on balls of different compositions is discussed. The possibility of replacing the costly chromium steel alloy balls by less costly mild steel balls is suggested. Some of the additives developed are found to be effective on balls of certain compositions while they are a total failure on the chromium steel balls. The studies reveal that some additives are effective on mild steel balls as well as chromium alloy steel balls. They can be very good substitutes for commercial additives with bearing balls of standard composition. As chromium alloy steel balls are much costlier there is a need to replace expensive alloy steel balls with cheaper low carbon steel balls, for certain specific purposes. This can be achieved by using suitable indigenous additives that are found to be effective on low carbon steel balls.     

Tribological evaluation and tribochemistry of some dialkyldithiomalonamides and their Mo‐S complexes as EP additives

The reported use of molybdenum dithiocarbamates and molybdenum dithiophosphates as antiwear and EP additives has led to attempts by the authors to synthesise certain novel Mo‐S complexes, and evaluate their effectiveness. In the present paper, the synthesis of certain 1,5‐dialkyl‐2,4‐dithiomalonamides and their Mo‐S complexes, namely, bis(1,5‐dialkyl‐2,4‐dithiomalonamido)‐dioxo‐molybdenum (VI), and the tribological evaluation of their 0.5% w/v admixtures in paraffin oil by a four‐ball test are reported, and the results compared with a dioxo‐bis(N,N‐diethyldithiocarbamato)‐molybdenum(VI) reference additive. The additive, bis(1,5‐diethylhexyl‐2,4‐dithiomalonamido)‐dioxo‐molybdenum(VI), has been found to reduce significantly both coefficient of friction and wear‐scar values, and to give higher load wear index values and flash temperatures, and has been found to be equally effective with alloy steel balls of three different compositions. However, all the Mo‐S complexes afforded smaller wear‐scar diameters in a one‐hour wear test. The wear spots on the used steel ball specimens were subjected to SEM and AES surface analysis for understanding the additive‐metal interaction tribochemistry.     

Metalworking additives: A new approach to EP properties

Work in the author's laboratory has shown that certain specially designed overbased sulphonate-compounds function as extreme pressure agents in heavy duty metalworking operations. Depending upon the application, these materials may be used individually or in combination with conventional EP agents; they have also shown a synergism with active sulphur compounds. Film strength tests, controlled tool life evaluations, and field trials confirm that high load-bearing properties are imparted to metalworking fluid formulations. In addition, we have seen dramatic effects on the quality of machined metal surfaces. As an extremely important benefit, these unconventional extreme pressure agents are environmentally acceptable.     

EP-efficient 1,2,4-dithiazolines and their tribological effect on steel bearing balls of different composition

This paper deals primarily with the potential extreme-pressure (EP) activity of certain cyclic disulphide additives in paraffin oil. The antiwear and antifriction properties of 1,2,4-dithiazo-line additives have been evaluated on a four-ball machine by using 12.7 mm diameter steel ball bearing specimen-I. The paper also includes a discussion on the effectiveness of 3-p-Cl-phe-nylimino-5-(N-methylphenyl)amino-1,2,4-dithiazoline on steel bearing balls of different compositions. The topography and the surface chemistry of the bearing ball wear scar were studied by Scanning Electron Microscopy (SEM) and Auger Electron Spec-troscopy (AES).     

EP activity evaluation of some 2-phenyl-3-phenylimino-5-arylimino-1,2,4-thiadiazolidines

A four-ball test was conducted to evaluate the EP activity of 2-phenyl-3-phenylimino-5-arylimino-1,2,4-thiadiazolidines (0.5% w/v) in paraffin base oil using a 12.7-mm diameter steel ball specimen. 2-phenyl-3-phenylimino-5-p-chlorophenylimino-1,2,4-thiadiazolidine exhibited good activity in reducing wear scar diameter and friction coefficient values at higher loads and increasing the values of flash temperature parameter (FTP), mean Hertz load (MHL) and pressure wear index (PWI) as compared with commercially available sulphur-phosphorous reference additives. The wear surface tribochemistry and topography were investigated using scanning Auger electron spectroscopy and scanning electron microscopy techniques.     

EP/AW performance evaluation of some zinc alkyl/dialkyl/alkylaryl‐dithiocarbamates in four‐ball tests

Tribochemistry, the chemistry of interacting surfaces under the influence of a lubricant, helps in the appropriate selection of suitable lubricant additives for specific uses. Modern lubricants are usually formulated from a range of petroleum base oils or synthetic fluids incorporating a variety of chemical additives for performance enhancement. Extreme‐pressure (EP) and anti‐wear (AW) additives are used extensively in lubricants for hypoid gears and metal cutting and forming operations to reduce wear, modify friction, and prevent scuffing of moving metallic parts. The present paper includes the synthesis and the evaluation of the tribological properties of 0.5% (w/v) solutions of some zinc bis‐(alkyl/dialkyl/alkylaryldithiocarbamates) in paraffin oil using 12.7 mm diameter steel bearing ball specimens in four‐ball tests. All the synthesised zinc dithiocarbamate additives in general, and zinc bis‐(morpholinodithio‐carbamate) (A₄) in particular, exhibited good AW, EP, and friction‐reducing properties. Additive A₄ especially gave low values of wear‐scar diameter and coefficient of friction at higher loads and higher values of load wear index and flash temperature parameter during EP tests (ASTM D 2783) and afforded lower values of wear‐scar diameter in a one‐hour wear test (ASTM D 2266–67). The surface topography of the wear‐scar matrix of the used ball specimens was investigated by scanning electron microscopy.     

基于成对双联角接触球轴承的摩擦力矩特性分析

对影响成对双联角接触球轴承精度和平稳度的摩擦力矩特性进行了分析研究.依据研究目的要求主要采用了试验验证和计算验证结合的试验方法.首先建立了特种轴承试验台系统.然后对成对双联角接触球轴承做了工况模拟和运转状态检测.从而得出了成对双联角接触球轴承变转速,变转向,变轴向载荷,变预紧力下的摩擦力矩曲线的大小和轴承曲线波纹度.进...     

A study of the tribological properties of some 1,3,4-thiadiazole type lubricant additives

The synergistic effects between the group containing S and P, hydroxyl group and a 1,3,4-thiadiazole ring in the same molecule have been studied by investigating the tribological properties of three 1,3,4-thiadiazole derivatives. The possibility of predicting properties of additives from their chemical structures is discussed. The results indicate that introducing a long carbon chain with a hydroxyl group (LCCWHG) into the side chains of a 1,3,4-thiadiazole ring can effectively enhance its antiwear ability and that dimercaptothiadiazole adduct of dialkyl thiaphosphoric acid (DAODTA) can have good extreme pressure performance and excellent antiwear properties.     

钢球表面粗糙度评定方法的探讨

通过对现行钢球表面粗糙度标准中和英国Talysurf轮廓仪说明书中有关参数的对比分析,对钢球表面粗糙度评定方法提出了新的看法。     

A study of elastohydrodynamic effects in a three-lobe journal bearing

The effect of flexibility of bearing liner on the static and dynamic performance characteristics of a three-lobe journal bearing was studied. The three-dimensional Navier-Stokes and the continuity equations governing the lubricant flow in the clearance space of the journal bearing, and the three-dimensional e elasticity equations governing the displacement field in the bearing liner, were solved by using the finite element method and an iteration scheme. The static and dynamic performance characteristics were calculated at various eccentricities for a wide range of values of deformation coefficients which take into account the flexibility of the bearing liner.     

Tribological study of a mannich compound of 2-mercaptobenzimidazole in liquid paraffin

Tribological study on a 12.7 mm diameter steel ball bearing specimen has been carried out in a four-ball machine using a potentially active heterocyclic additive in liquid paraffin. The synthesis of 2-(di-n-butylaminomethyl) thiobenzimidazole is described. The 2-(di-n-butylaminomethyl) thiobenzimidazole has been found to be quite effective as a potential additive in liquid paraffin according to the results. Employing X-ray photoelectron spectroscopy, the film formed when the additive reacted with the metal was investigated.     

角接触球轴承的温度场分析

研究轴承的发热、传热过程,可为轴承动态油膜的热失稳研究提供理论支持。建立滚动轴承油气或油雾润滑下的热节点传热模型,利用热网络法建立温度场计算模型,并考虑轴承转速、载荷、离心力和自旋对温升的影响,计算出各节点的温度。结果表明,角接触球轴承的热生成与轴承转速、载荷、离心力和自旋有关,转速越高,载荷越大,则轴承的温升越高;随着转速增大,离心力和自旋对温升的影响增大,尤其高速情况下,离心力和自旋对轴承温升的影响不可忽略。     

A comparative study of the thermal behaviour of profile bore bearings

This paper describes principally a theoretical analysis of the thermal behaviour of offset half, orthogonally displaced, three-lobe and four-lobe bearing geometries. The thermal analysis illustrates the implication of type selection with regard to the parameters of load-carrying ability, power loss, lubricant requirements and operating temperatures. The comparisons show that for all profiles considered, they have inferior load-carrying ability when compared with the cylindrical geometry along with significantly larger lubricant supply requirements. Thermal effects in profile bore bearings are less extreme than those encountered in the cylindrical profile.     

混合陶瓷球轴承在微型涡喷发动机中的应用

以WP25微型涡喷发动机为研究对象,对混合陶瓷球轴承在微型涡喷发动机中的应用进行了试验研究.利用有限元计算与试验验证相结合的办法,确定了转子的临界转速范围;指出混合陶瓷球轴承在高温、高速条件下的失效形式以表层金属脱落为主,同时提出了改进措施,为混合陶瓷球轴承在微型涡喷发动机中的应用提供了参考依据.     

Microstructure Characterization of Degraded Grease in Axle Roller Bearings

Abstract

Aged mineral-oil-based, lithium-hydroxystearate-thickened grease was collected from used axle spherical roller bearings, which were used for urban commuter trains. Three types of aged grease were categorized based on the total distance that the bearing had traveled, as early life (<0.05 million km [M.km]), medium (0.3–0.6 M.km), and heavily used (1.82 and 2.0 M.km). The microstructure of degraded grease from 20 bearings was characterized in this project using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Base oil of each grease sample was released by a centrifugation method and the oxidation of bled oil was measured by infrared analysis. A notable change in grease microstructure was observed by AFM and SEM. The thickener morphology changed from an entangled helical fibril structure to particle-like nanofragments. The variation in thickener microstructure was observed in the early life grease, which suggested grease can experience an inconsistent aging process in the real-life bearings. Overall, 70.5?±?1.37?wt% base oil bled from the fresh grease, 68.2?±?0.73?wt% from the early life grease, 58.1?±?2.33?wt% from the medium used grease, and 60.0?±?6.35?wt% from the heavily used grease. The results suggest that the densely packed microstructure observed in the aged grease affects the capability of base oil bleeding from the grease. The retardation of base oil flow due to degraded grease may result in the lubricating ability of grease becoming compromised and hence result in an increased wear rate of the bearings.     

A study of thermohydrodynamic lubrication in a circular journal bearing

An analytical method to determine the film temperature of circular journal bearings was developed, which considers the cavitation of the oil film and also recirculation and mixing of the lubricant. The results were verified experimentally. The theory is in good agreement with experiment over a wide range of operating conditions. The effects of journal speed, clearance ratio, lubricant viscosity and specific load on the bearing temperature were examined, and the following conclusions derived. (1) T_b,max, the maximum temperature on the bearing metal surface, increases considerably with the increase of speed and lubricant viscosity and with the decrease of clearance ratio. (2) With the increase of speed, the angular position of T_b,max varies considerably towards the direction of journal rotation from the upper stream side of the location of minimum film thickness, h_min, to the lower stream side of it. The change of angular position of T_b,max is greater than that of h_min. The contrary happens with decrease of the clearance ratio. (3) These characteristics of T_b,max correspond to those of the maximum temperature, T_f,max, in the oil film.     

Synthetic aluminium complex grease: A tribological evaluation using a four‐ball test

This paper describes the preparation and performance evaluation of a synthetic aluminium complex grease. The aluminium complex grease was prepared in situ by reacting stearic acid and benzoic acid in the presence of a synthetic base oil, polyalphaolefin. The preparation of the soap (aluminium benzoate stearate hydroxide) was monitored using Fourier transform infrared. Two different extreme‐pressure additives blended with the prepared aluminium complex grease were evaluated for their extreme‐pressure activity in four‐ball and Timken tests. These greases exhibited higher Timken OK loads (60 lb), lower values of wear‐scar diameter at higher loads, and higher values of weld load in the four‐ball test than the aluminium complex grease without additive. The blended greases were also found to pass rust and corrosion, oxidation‐stability, and shear‐stability tests. The topography of the specimens after four‐ball testing was studied with scanning electron microscopy.     

Fungal mediated synthesis of silver nanoparticles and evaluation of antibacterial activity

Nanoparticles as biomedicine has made a crucial role in health biotechnology. Different transition metals in various forms playing role in nanotechnological advances and biological applications. Silver as one of the nontoxic, safe inorganic antibacterial agents and can serve as replacement of antibiotics. Present research is based on biogenic synthesis of silver nanoparticles (Ag‐NPs) as potential antibiotics from fungal metabolites of Penicillium oxalicum. We used different analytical techniques X‐ray diffraction (XRD) and scanning electron microscopy (SEM) for characterization of biosynthesized silver nanoparticles. Furthermore, the antibacterial activity of biosynthesized silver nanoparticles was checked against Staphylococcus aureus, S. dysenteriae, and Salmonella typhi by using well diffusion method and UV visible spectrophotometer. Maximum zone of inhibition recorded against S. aureus, Shigella dysenteriae was 17.5 ± 0.5 mm (mm) for both species and 18.3 ± 0.60 mm for Salmonella typhi. The biosynthesized silver nanoparticles of P. oxalicum showed excellent antibacterial activity. It was concluded from our results that biosynthesized silver nanoparticles have significant potential and might be useful for a wide range of biological applications such as bactericidal agent against resistant bacteria, preventing infections, healing wounds, and anti‐inflammation.