Emulsion Lubrication Research Articles

A novel laser-induced fluorescence concept for thermometry measurements in machining lubricoolants

This study investigates a two-colour laser-induced fluorescence (LIF) technique for thermometry in cooling lubricants (CL) for machining. The diagnostic technique should enable a simultaneous determination of cooling film thickness and film temperature, which is relevant for typical machining processes like turning and milling processes. The temperature determination is based on a temperature-sensitive fluorescence intensity ratio of a special dye determined in suitable spectral regions representing common band pass filters. For this purpose, two CL emulsions CL6 (6 vol.% CL, 94 vol.% water; normal machining) and CL10 (10 vol.% CL, 90 vol.% water; heavy machining) and its individual components were doped with the fluorescence dye Eosin-Y. Temperature dependent spectral LIF intensities were recorded in the range of 273–313 K, which are relevant for milling and cutting operations. Furthermore, absorption spectra were analysed as well. The temperature-dependent fluorescence measurements revealed a temperature limit for the emulsion stability. The emission peaks of Eosin-Y are shifted with increasing temperature towards longer wavelengths. The sensitivities of CL10 (1.88%/K) and CL6 (1.58%/K) are comparable to or even higher than the sensitivities of other LIF dyes provided in the literature. The literature-based dyes were however not determined in those CL. The measurements showed, that the investigated tracer-CL/water emulsions mixed with the dye enable a reliable temperature determination.

Wear analysis and life prediction of sucker rod and tubing under ternary emulsion lubrication in Daqing oilfield: a case study in block H

Daqing Oilfield as the world’s largest application area of alkali–surfactant–polymer (ASP) flooding, in recent years, with the increase in aging wells, the eccentric wear and deformation of sucker rod and pipe during oil production has become more and more serious. In order to study the effect of emulsion lubrication in ternary composite flooding on eccentric wear of sucker rod and tubing, this paper establishes a calculation model for the depth of tubing wear under different emulsion lubrication conditions through indoor friction and wear experiments combined with White and Dawson wear efficiency theory. Based on this, the finite element method is used to predict the safe wear life of tubing under different component emulsion lubrication. The results show that compared to intact oil pipes, the residual internal pressure strength of oil pipes with defects decreases, and stress concentration occurs at the edges and middle of the defects. The wear life of oil pipes decreases with the increase in pump depth and wear coefficient under emulsion lubrication. The water content and alkali concentration have the most significant effects on the wear life of oil pipes under emulsion lubrication conditions. The safe wear life of sucker rod pipes under emulsion lubrication with a water content of 75% will be increased by 37.8% compared to those in emulsion lubrication with a water content of 95%, and under emulsion lubrication with an alkali concentration of 500 mg/l, the safe wear life will be increased by 50.6% compared to those in emulsion lubrication with a concentration of 2000 mg/l. The research results can provide theoretical and technical support for oilfield enterprises to reduce rod and pipe wear in ASP flooding oil wells, improve the pump inspection cycle of pumping wells, and ensure the safety of oil well work.

A monosurfactant-stabilized dual-responsive and versatile emulsion lubricant

Emulsions consisting of lubricating base oil and water have extensive applications in the fields of metalworking and heavy-duty machinery. Due to the compositional complexity that confines an effective recycling of emulsion constituents and the frequent use of toxic, non-biodegradable mineral base oil, an industrial emulsion lubricant is usually easy to produce severe environmental burdens and health issues. Here we report a dual-responsive and versatile lubricating emulsion solely consisting of water, an eco-friendly ester base oil and a synthetic cationic emulsifier. Taking advantage of the inclusion of azobenzene moiety, [CeCl3Br]- anion and methylimidazole head-group, the surfactant can not only undergo tribochemical reactions to function as a lubricant additive to achieve very low interfacial friction, but also endow the resulting emulsion efficient anticorrosion, antibiosis and both light- and magneto-responsiveness. Based on a reversibly photo-triggered variation in the hydrophobicity of surfactant, an on-demand separation and recycling of emulsion component followed by a nearly one order of magnitude conversion in the friction can be realized. Together with its magneto-controlled migration and adaptivity to high normal loads, we envision that the emulsion lubricant may find potential applications in a broad range of industrial systems requiring lubrication and heat dissipation as well as smart devices needing control over the friction between two contacting surfaces.

A novel powder-metallurgical eco-friendly recycling process for tool steel grinding sludge

This work comprehensively investigates the reuse of AISI D2 tool steel grinding sludge as secondary raw material into a powder metallurgical process route. The tool steel grinding sludge initially contains about 15 mass% of silicon carbide and aluminium oxide abrasive particles as well as residual cooling lubricant emulsion consisting of water and oil leading to an increased carbon content of 2.56 mass%. A three-stage decontamination procedure of the grinding sludge is performed, including drying, removing non-metallic abrasive particles via magnetic separation, and recovering the cooling lubricant oil by supercritical carbon dioxide extraction. Subsequently, the prepared grinding metal chips are densified by a novel energy efficient short-time sintering technique called electric discharge sintering. The carbon content of the sludge could be reduced to 1.71 mass%. However, it was found that remaining contaminations lead to a change in the alloying composition of the recycled material, which influences the tempering behavior. Increased carbon and silicon levels promoted a high retained austenite fraction after quenching of more than 67 vol%. By adopting the heat treatment, the hardness of the recycled samples could be adjusted to a level similar to that of the cast reference material in quenched and tempered condition. Reducing the retained austenite content to 2.3% by tempering led to a hardness of roughly 700 HV1.However, the recycled material showed less than 40% of the compressive strength of the cast reference material. On the one hand, the lower compressive strength can be attributed to the inadequate removal of oxidic abrasive particles during the recycling process and their poor integration into the metal matrix of the compacted specimens. In addition, oxidized layers on the chip surfaces counteract metallurgical bonding between the chips during electric discharge sintering.

Expanding the applicability of ASTM D3233A Pin & Vee Block method to evaluate lubricant emulsions for cutting applications

ABSTRACT ASTM Method D3233A uses a Pin&Vee Block tester to evaluate cutting fluids. However, the standard defines a steel-steel contact, uses a small volume of lubricant, and the test report is limited to the ‘ultimate failure load’. With our approach, we bring testing closer to reality, using different metallurgies and testing the oils in aqueous emulsion-form. We monitor the frictional torque throughout increasing load, so that differences between products are revealed that are not visible in failure load alone. By modifying lubrication to recirculated or misted conditions, we simulate cutting of forming operations. Consequently, this provides an additional tool for cost efficient ranking of cutting fluids, based on an industry-accepted instrument. We demonstrate same ranking of cutting fluids as well established Tapping Torque Tests, with the advantage of using a simplified and lower cost configuration. Developing a standardized test protocol involves more work on reproducibility and correlation to real machining processes.

Modeling Electrocoagulating Purification of Spent Washing Liquids to Remove Emulsified Lubricating Oils

The possibility of electrocoagulating purification of spent washing liquids (SWL) from emulsified lubricating oils was verified. Using this technology, railway car-repair depots would be able to organize the recycling systems for repeated use of refined SWL and for isolated lubricants utilization. The purification of real SWL was simulated with faint direct current (DC) exposure on the lubricant emulsions (SWL imitations).

Experimental study on the tribological properties of high water-based piston friction pairs with different ceramic materials

The effects of load and reciprocating frequency on reciprocating sliding of ZrO2/steel, Si3N4/steel, and SiC/steel under high water-based emulsion lubrication were studied by the ball-block sliding tester, including a series of tribological behavior and wear mechanisms. Through the analysis of the above characteristics, determine the influence of load and frequency on the friction and wear properties of the ceramic/steel friction pair. The results show that with the increase of load, the friction coefficient of the three ceramic friction pairs decreases, and the wear rate increases continuously. With the increase of frequency, the friction coefficients of ZrO2/steel and Si3N4/steel steadily decrease, the friction coefficient of SiC/steel increases slightly, and the wear rates of the three friction pairs decrease continuously. The comprehensive comparison shows that the ZrO2/steel friction pair shows the best tribological performance under different working conditions, which is more suitable for the friction pair material of high water-based hydraulic components, and the Si3N4/steel friction pair shows better wear resistance when the load is above 50 N.

Enhancement of Deep Drilling for Stainless Steels by Nano-Lubricant through Twist Drill Bits

This paper represents a new lubricant method which is able to one-stroke drill deep holes with a length-to-diameter of 8, on the AISI SUS 304 stainless steel. By adding graphene nanosheet into typical soluble emulsion and then mixing with water, a nano fluid can be made. The results revealed that using nanofluid can provide a reduction of 4.4-fold of the drilling torque, and thus expand the tool life as many as 20 times, compared with using typical emulsion lubricant. The proper set of cutting parameters was found by using Taguchi L9 experiments as 550 rpm spindle speed and 0.05 mm/rev. The results can be expanded to apply in other deep drilling of hard-to-cut material, using inexpensive devices and avoiding peck-drilling. The proposed lubricant can also be promissing for other machining operations.

Modification strategies of polyacrylonitrile ultrafiltration membrane using TiO2 for enhanced antifouling performance in water treatment

The active application of ultrafiltration in various industries requires the development of novel membranes with tailored properties and good fouling resistance. This work is devoted to the improvement of ultrafiltration properties of polyacrylonitrile (PAN) membranes by various TiO2 modification approaches: (1) ex situ method - the introduction of pre-formed micro- or nanoparticles; (2) in situ method - the formation of TiO2 particles in the casting solution; and (3) surface modification method - dynamic deposition of TiO2 on the membrane surface. The effect of the various TiO2 immobilization techniques on the structure of PAN membranes was studied by scanning electron and atomic force microscopies, and the contact angle measurements. The introduction of TiO2 particles improved membrane performance and antifouling stability under UV irradiation in ultrafiltration of industrially important feeds - bovine serum albumin solution (BSA) and coolant lubricant emulsion. The affinity to water of TiO2-modified PAN membrane was confirmed by atomistic molecular dynamics simulations, swelling experiments, and calorimetric study of wetting. PAN membrane with 0.5 wt% TiO2 nanoparticles had the optimal transport characteristics and improved surface self-cleaning ability after UV irradiation: pure water, coolant lubricant, and BSA fluxes (849, 38, and 68 L/(m2h), respectively), and flux recovery ratio after UV-illumination (95%).

Novel High Flux Poly(m-phenylene isophtalamide)/TiO2 Membranes for Ultrafiltration with Enhanced Antifouling Performance

Wide application of ultrafiltration in different industrial fields requires the development of new membranes with tailored properties and good antifouling stability. This study is devoted to the improvement of ultrafiltration properties of poly(m-phenylene isophtalamide) (PA) membranes by modification with titanium oxide (TiO2) particles. The introduction of TiO2 particles improved membrane separation performance and increased antifouling stability and cleaning ability under UV irradiation. The developed membranes were characterized by scanning electron and atomic force microscopy methods, the measurements of water contact angle, and total porosimetry. The transport properties of the PA and PA/TiO2 membranes were tested in ultrafiltration of industrially important feeds: coolant lubricant (cutting fluid) emulsion (5 wt.% in water) and bovine serum albumin (BSA) solution (0.5 wt.%). The PA/TiO2 (0.3 wt.%) membrane was found to possess optimal transport characteristics in ultrafiltration of coolant lubricant emulsion due to the highest pure water and coolant lubricant fluxes (1146 and 32 L/(m2 h), respectively), rejection coefficient (100%), and flux recovery ratio (84%). Furthermore, this membrane featured improved ability of surface contamination degradation after UV irradiation in prolonged ultrafiltration of BSA, demonstrating a high flux recovery ratio (89–94%).

Environmentally sustainable cooling strategies in milling of SA516: Effects on surface integrity of dry, flood and MQL machining

Abstract The recent move towards ‘Environmentally Sustainable Manufacturing’ (ESM) is leading heavy industries (e.g. oil & gas, nuclear) to explore low-impact manufacturing strategies. In machining, however, most processes are still performed using traditional cooling method using flood or high pressure lubricant emulsions. These emulsions are expensive in their maintenance and disposal, and present a significant environmental concern. This novel study combines evaluations of the performance of low-impact cooling strategies, such as dry milling or minimum quantity lubrication (MQL), in the manufacture of an industrially important pressure vessel carbon steel (SA516) using coated carbide inserts. Tool wear, surface roughness, residual stress and energy consumption were measured during metal cutting trials for each strategy and then compared. Likely tool wear performance when using candidate lubricants was screened prior to machining trials using standard tribological high frequency reciprocating tests. Significant improvements in surface integrity and tool wear were observed when machining with dry and MQL when compared with traditional flood coolant. Measured energy footprints for dry and MQL were also lower when compared to flood coolant machining providing cost savings and environmental advantages in manufacturing using ESM approaches.

Quality assessment of milling technology and the biocidal effects of SiO2 or TiO2 nanoadditives in cooling lubricant emulsions

Nanoparticles (NPs) of TiO2 or SiO2 (size of 10–25 nm) added to a cooling lubricant emulsion (CLE) have a positive effect on the machining process due to a reduction in the average friction coefficient, a reduction in the variance of the measured values and a reduction in the wear of the cutting tool resulting in increased durability. The functional properties of NPs were evaluated using two different CLEs – CLE1 with the majority content oxygen molecule and various amines; and CLE2 composed of oxygenated organic compounds comprising glycols and higher alcohols. Conventional face milling was selected as the machining process type with the cutting speed 119 m min−1; rotor speed 600 rpm; feed per tooth 0.1 mm; feed rate per minute 60 mm; depth of cut 1 mm and width of cut 40 mm. The addition of spherical SiO2 NPs and TiO2 NPs with a flat surface texture with smooth edges led to a reduction in wear, in the sticking region there was no evidence chipping, cracking or peeling of the coating. The different compositions of CLE1 and CLE2 influence the biocidal effects of the NPs on bacteria cells; CLE1 with SiO2 of 56.6%, and with TiO2 of 18.4%; CLE2 with SiO2 of 26.5%, and with TiO2 of 55.3%. The presence of NPs in the CLEs does not increase the cytotoxic effect on mouse fibroblast cells; however, the composition of CLE1 and CLE2 affects the cytotoxicity for mouse fibroblast cells; CLE1 has an up to 59.6% higher cytotoxic effect than CLE2.

High-throughput toxicity study of lubricant emulsions and their common ingredients using zebrafish.

Though lubricant emulsions have been widely used in many industrial processes, various human health hazards have been reported. Conducting a systematic toxicity study on emulsions is difficult since emulsions contain multiple chemical compounds, and hydrophobic compounds form complex emulsion particles via surfactants. For a quantitative toxicity study, we developed a high-throughput imaging system using zebrafish and conducted a large scale in vivo toxicity assay of lubricant emulsion and their common ingredients. By computing the locomotion activity of zebrafish from captured time-lapse images, we could quantify the degree of relative toxicity of 29 chemicals. The changes in the locomotion activity over time were observed to vary significantly depending on emulsions, indicating that the degree of toxicity of the commercial products was very diverse. We found that primary ethanolamines were more toxic than secondary or tertiary ethanolamines, and several factors, such as alkyl chain length, EO mole, test concentration, and emulsion particle size, affected toxicity.

High-Speed Drawing of Al Alloy Wire by Diamond-Coated Drawing Die Under Environmentally Friendly Water-Based Emulsion Lubrication

It is environmentally friendly to use water-based emulsion instead of the oil when cold drawing Al alloy production. In this research, adopting specially prepared water-based emulsion, contact angles and tribological properties of as-selected multilayer diamond films are clarified. The contact angle on diamond film is much smaller than that on WC-Co with the same surface roughness, and tribological behaviors of the diamond film are much better. The effects of surface roughness Ra of the film, lubrication, and water content in the emulsion W are studied, indicating that the contact angle increases with W or Ra. For the diamond film, lower Ra is beneficial for reducing the coefficient of friction (COF), Al alloy ball wear and oxidation, while lower W contributes to the reduction of the COF, ball oxidation, and coated disk wear. Finally, high-speed drawing of high-quality 6021 Al alloy wires (AWs) is accomplished, proving that using coated drawing dies, the water-based emulsion (W < 80 vol %) can totally replace oil, and coated dies under the water-based emulsion lubrication present much elongated lifetime and can guarantee the production quality, compared to uncoated ones under the oil lubrication, in spite of slightly severer wire oxidation.

Novosphingobium lubricantis sp. nov., isolated from a coolant lubricant emulsion.

A yellow-pigmented, Gram-stain-negative, rod-shaped, non-spore-forming bacterium (strain KSS165-70T) was isolated from a coolant lubricant emulsion. The 16S rRNA gene sequence analysis of strain KSS165-70T showed high sequence similarity to the type strains of Novosphingobium subterraneum (98.1 %), Novosphingobium lentum (97.9 %) and Novosphingobium taihuense (97.8 %). Sequence similarities to type strains of all other Novosphingobium species were below 97.5 %. Ubiquinone Q-10 was detected as the major respiratory quinone. The predominant fatty acid C18 : 1ω7c and the typical 2-hydroxy fatty acid C14 : 0 2-OH were detected. The polar lipid profile contained the major lipids diphosphatidylglycerol, phosphatedylethanolamine, sphingoglycolipid, phosphatidylcholine and two unidentified phospholipids. The polyamine pattern contained the major compound spermidine. Characterization by 16S rRNA gene sequence analysis, physiological parameters, pigment analysis, and ubiquinone, polar lipid and fatty acid composition revealed that strain KSS165-70T represents a new species of the genus Novosphingobium. For this reason, we propose the name Novosphingobium lubricantis sp. nov. with the type strain KSS165-70T (=CIP 111490T=CCM 8814T).

Tribological properties of diamond films for high-speed drawing Al alloy wires using water-based emulsions

Abstract Tribological tests are conducted on diamond films under different lubrications, and influences of film type, lubrication, test parameters on coefficient of friction (COF) and film wear (Id) are studied. Diamond films perform better than WC-Co under water-based emulsion lubrication, and the boron doped micro-crystalline and nano-crystalline composite diamond (BDMC-NCCD) film shows the best overall behavior. Considering the performance and economy, the water content in the emulsion is optimized as about 80 vol%. Under this drawing condition, the quality of the production is similar to that drawn by the uncoated dies under the oil lubrication, however, the coated dies present much prolonged lifetime and lower temperature. Most importantly, the use of the water-based lubrication is much more environmentally friendly.

Surface Film Adsorption and Lubricity of Soybean Oil In-Water Emulsion and Triblock Copolymer Aqueous Solution: A Comparative Study

This paper investigates the surface film adsorption and lubricity of two different types of potential environmentally friendly cold metal forming lubricants: soybean vegetable oil in water VO/W emulsions and triblock copolymer aqueous solutions. The lubricants have different visual appearance, surface film adsorption characteristic, lubricity and surface cleaning behaviour. The effects of concentration, temperature and emulsification ultrasonic energy (for VO/W emulsion) are studied. The result shows that the soybean VO/W emulsions have stronger adsorption, superior lubricity and anti-wear property compared to the copolymer solutions. The effect of temperature is investigated at 30 °C and 65 °C which are below and above cloud point of the aqueous copolymer solutions. Both lubricants show improved friction and anti-wear property at 65 °C. However, tenacious residual film remained on the discs surface after surface cleaning indicates lower cleanability of the soybean VO/W emulsions compared to the copolymer solutions, postulating the need for extra post-processing cleaning operations after cold forming process with VO/W emulsion lubricant.

The emulsifying and tribological properties of modified graphene oxide in oil-in-water emulsion

Graphene oxide (GO) was asymmetric chemically modified with myristyltrimethylammonium bromide (TTAB) to get modified graphene oxide (MGO). This MGO was used as an emulsifier and additive in oil-in-water emulsion. The emulsifying tests showed MGO greatly improved the stability of base emulsion and decreased its droplets size. Tribological test results showed that under the boundary lubrication condition with MGO-emulsion, the friction coefficient (COF) and the wear rate of the steel ball were decreased by about 18% and 48% respectively, comparing with base emulsion lubrication. The tribological mechanism of MGO-emulsion could be explained by the strong film-forming ability on the metal surface; the good lubricity of its small droplets; the formed adsorption film, transfer film and tribofilm between the contact surfaces.

Modeling of heat transfer conditions in cooling lubricant emulsions with low-boiling continuous media in narrow gaps

The article analyzes the behavior of the cooling lubricant emulsions of oil-in-water type in a limited volume of narrow gaps. Vapor phase which has been generated by heating the emulsion to a temperature that exceeds the boiling point of water, modifies substantially the conditions of interaction between the dispersed droplets of oil with friction surfaces. Nucleation and growth of vapor bubbles stimulates heat transfer due to the pulsating character of motion of the emulsion and associated with it breakup of the oil droplets. A model of “hot” turbulence has been proposed in the double emulsion of the dispersed phase (oil and steam), initiated by the growth of vapor bubbles. In order to assess the effectiveness of the cooling lubricant emulsion, the mechanisms of hydrodynamic fragmentation of droplets of lubricating oil under conditions of narrow gaps were taken into account. The model was used to estimate the empirical constants in the dependence of the critical temperature from volumetric concentration of oil for AA 5182 aluminum cooling lubricant emulsion E1 (Januszkiewicz et al., 2004), separating the lubrication regime from the “dry” slip regime. It was shown that the model estimates are in good agreement with the experimental data. Therefore, the obtained results indicate that the model representations of this work do not contradict the physical nature of the complex process of heat transfer.

Insight into the role of amines in Metal Working Fluids

The influence of primary/tertiary amines in Oil-in-Water emulsions (as Metal Working Fluids (MWFs) towards brass) is evaluated in both pure water and 5% O/W emulsion. Physical properties, wetting, lubricating and corrosion behaviors are finely investigated. Experimental results show that the number of carbon atoms in amines plays a pivotal role in reducing the brass corrosion. Among the adopted amines, the cyclohexyldiethanolamine (CHDEA) seems to be the optimal one in both media: (i) it adsorbs easily onto the brass limiting corrosion and stain; (ii) it leads to stable emulsions; (iii) it does not affect the emulsion lubricant and wetting performances.