Water-based Lubricant Research Articles

Triboelectrochemical friction control of W- and Ag-doped DLC coatings in water-glycol with ionic liquids as lubricant additives.

In the last years, diamond like carbon (DLC) coatings doped with both carbide forming and non-carbide forming metallic elements have attracted great interest as novel self-lubricating coatings. Due to the inherent properties of DLC, the doping process can provide adsorption sites for lubricant additives depending on the chemical and electrochemical state of the surface. Ionic liquids (ILs) are potential lubricant additives with good thermal stability, non-flammability, high polarity, and negligible volatility. These characteristics make them also ideal for polar fluids, like water-based lubricants. In this work, three different DLC coatings (DLC, W- and Ag-doped DLC) were deposited on stainless steel substrates and their friction in dry and lubricated conditions in water-based lubricants was studied. Three ILs, tributylmethylphosphonium dimethylphosphate (PP), 1,3-dimethylimidazolium dimethylphosphate (IM) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP) were used as additives and compared with a well-known organic friction modifier (dodecanoic acid). The results showed better mechanical integrity, toughness and adhesion of the doped coatings compared to the undoped DLC. The Ag-doped DLC coating had the best mechanical properties of all the coatings. W formed tungsten carbide precipitates in the DLC coating. Two different additive-adsorption mechanisms controlled friction: a triboelectrochemical activation mechanism for Ag-DLC, and an electron-transfer mechanism for W-DLC resulting in the largest reduction in friction.

Advanced developments in environmentally friendly lubricants for water-based drilling fluid: a review.

The problem of high friction and high torque is one of the most troublesome problems for engineers in extended reach wells and long horizontal wells. Generally, the friction coefficient of oil-based drilling fluid is around 0.08, while the friction coefficient of water-based drilling fluid exceeds 0.2, which is much higher than that of oil-based drilling fluid. With the increasingly stringent environmental regulations, water-based drilling fluids have gradually become a better choice than oil-based drilling fluids. Therefore, lubricants become a key treatment agent for reducing the friction coefficient of water-based drilling fluids. Although there have been many related studies, there is a lack of comprehensive reviews on environmentally friendly water-based drilling fluid lubricants. In general, water-based drilling fluid lubricants can be mainly divided into solid lubricants, ester-based lubricants, alcohol-based lubricants, and nano-based lubricants. Vegetable oil ester-based lubricants, biodiesel lubricants, and dispersible nano-lubricants are all promising environmentally friendly water-based drilling fluid lubricants. Understanding the lubrication mechanism of different types of lubricants and clarifying the evaluation methods of lubricants is an important prerequisite for the next development in high-performance water-based drilling fluid lubricants. Therefore, the purpose of this paper is to give a comprehensive overview of water-based drilling fluid lubricants in recent years, in order to fully understand the development and lubrication mechanism of water-based drilling fluid lubricants, and provide new ideas for subsequent research on water-based drilling fluid lubricants.

Zwitterionic Dopamine Sulfonate Functionalized Carbon Quantum Dots as Water-Based Lubricant Additive for Friction and Wear Reduction

Zwitterionic Dopamine Sulfonate Functionalized Carbon Quantum Dots as Water-Based Lubricant Additive for Friction and Wear Reduction

Study of Tribological Properties of Fullerenol and Nanodiamonds as Additives in Water-Based Lubricants for Amorphous Carbon (a-C) Coatings.

The tribological performances of fullerenol and nanodiamonds (NDs) as additives in water-based lubricants for amorphous carbon (a-C) coatings are investigated to avoid disadvantage factors, such as chemical reactions and deformation of particles. The effects of size and additive amount on tribological properties of nanoparticles are studied by rigid nanoparticles within the dot size range. The results show that owing to its small particle size (1–2 nm), fullerenol cannot prevent direct contact of the friction pair at low concentration conditions. Only when the quantity of fullerenol increased to support the asperity contact loads in sufficient concentration did nano-bearings perform well in anti-friction and anti-wear effects. Unlike fullerenol, nanodiamond particles with a diameter of about 5–10 nm show friction-reducing effect based on the nano-bearing effects at ultra-low concentration (0.01 wt.%), whereas particles at higher concentration block the rolling movement, hence increasing the coefficient of friction (COF) and wear. As a result of the effect of difference in size, fullerenol provides a better overall lubrication, but it is hard to reach a friction coefficient as low as NDs even under the optimal conditions.

Enhanced lubricity and anti-wear performance of zwitterionic polymer-modified N-enriched porous carbon nanosheets as water-based lubricant additive

The zwitterion polymer functionalized N-enriched porous carbon nanosheets were prepared via pyrolysis and etching of pyridine-coordinated polymer for N@PCNS. Subsequently, N@PCNS was modified with polydopamine to grow the zwitterionic polymer (PEIS), thereby acquiring PEIS functionalized N@PCNS (PEIS-PCNS). The exceptional tribological performance of PEIS-PCNS was attributed to the synergistic lubrication effects of N@PCNS along with the zwitterionic polymer PEIS, which facilitates the formation of a stable protective carbon film over the worn surface via complicated tribo-chemical reaction. Meanwhile, the presence of a hydration layer encapsulated by PEIS as the boundary lubricating film proves highly conducive for friction reduction. The average coefficient of friction showed a dramatic decrease to 0.17 from 0.63, and the wear depth of stainless steel dropped 64%.

Polydopamine-stabilized ZIF-8: Improved water stability and lubrication performance

ZIF-8, a novel lubricant additive, is considered to have great potential in reducing friction and wear due to large specific surface area, thermal stability and mechanical flexibility. However, ZIF-8 nanoparticles readily hydrolyze in aqueous solutions, transforming into large-sized lamellar and rod-like materials, which is a major bottleneck as a water-based lubricant additive. Herein, a strategy is proposed to functionalize ZIF-8 via mussel-inspired polydopamine (PDA) polymerization process to improve its lubrication stability in the water phase. The modified ZIF-8 (PDA@ZIF-8) can firmly “locked” water molecules on the surface of PDA to protect internal structure of ZIF-8, and improve its dispersion and stability of ZIF-8 in water. Moreover, ZIF-8@PDA tribofilm and iron oxide chemical protection film are formed during the friction process, and the low shear strength water layer between the contact surfaces contribute to achieving powerful synergistic lubricating effects, resulting in friction coefficient and wear track width reduce by 65% and 66%, respectively. Therefore, this work provides a promising alternative for expanding the practical application of ZIF-8 in aqueous environment and tribology.

Ionic liquids as boundary additives in water-based and PAO lubricants

Ionic liquids have been widely discussed as potential lubricants, however, their properties make them also very good potential candidates as lubricant additives (e.g., friction modifiers and anti-wear). In this work, the tribological study of two ionic liquids (tributylmethylphosphonium dimethylphosphate (PP), and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP)) as lubricant additives has been performed on stainless steel (AISI 316L) exposed to polar (water-glycol) and non-polar (polyalphaolefin) based lubricants under boundary lubricating conditions. The performance of these ionic liquids as lubricant additives has been compared to a classical organic friction modifier (dodecanoic acid (C12)). The water-glycol lubricant formulated with the two ionic liquids showed friction values higher than the same base lubricant formulated with dodecanoic acid, however, opposite results were observed for polyalphaolefin (PAO). A detailed surface chemical analysis using X-ray photoelectron spectroscopy (XPS) revealed differences in the passive/tribofilm thickness and chemical composition of the stainless steel surface tested in all lubricants. In the case of the polar lubricant additivated with ionic liquids, the tribochemical reaction accompanied by a tribocorrosion process led to the formation of an unstable passive/tribofilm resulting in high friction and wear. However, in the absence of tribocorrosion process (polyalphaolefin base lubricant), the tribochemical reaction led to the formation of a stable passive/tribofilm resulting in low friction and wear. A detailed surface and subsurface investigation of the microstructure using scanning electron microscopy equipped with a focused ion beam (SEM-FIB) showed that high wear rates resulted in thicker recrystallization region under the wear track surface. Among all lubricant additives tested in this work, BMP in non-polar lubricant media showed the best tribological performance.

A molecular dynamics study on the synergistic lubrication mechanisms of graphene/water-based lubricant systems

Water-based lubricants with graphene have excellent lubrication behaviors, but the synergistic mechanism involving the activities of both water and graphene isblue still unclear. This work investigates such mechanism by considering the effect of different factors such as the number of water molecules, loading, surface roughness and sliding velocity via molecular dynamics simulation. It is found that the friction reduction by water-based lubricants is due to the enhanced isolation between friction pairs by the graphene presence and the improvement of water replenishment. The synergistic lubrication mechanism works as that the water molecules may protect the structural integrity of graphene by inducing its movement to release lateral stresses and the graphene can enhance the movement of water molecules and promote their rolling like bearings.

Alkyl glyceryl ethers as water-based lubricant additives in mixtures with xanthan gum

Water-based lubricants are greener and more environmentally friendly than comparable oil-based lubricants. However, water-based lubricants typically have a poorer performance and, thus, need to be formulated with various additives. Here, alkyl glyceryl ethers, a class of nonionic surfactants, were investigated as lubricant additives. To this purpose, aqueous solutions of newly synthesized ethers (with different alkyl chain lengths, C8, C10, C12, and C14) were formulated with xanthan gum. The lubrication performance of these formulations was then tested experimentally. Clearly, alkyl glyceryl ethers showed a significantly improved performance (higher friction reduction) with increasing the alkyl chain length. However, the ethers had to be formulated with xanthan gum, with which they formed a complex, which promoted ether dispersion and probably adsorption on the metal surface in the aqueous phase, thereby drastically reducing friction. Thus, the alkyl glyceryl ethers synthesized in this work are attractive green and highly efficient lubricant additives, which can improve the sustainability of industrial lubrication processes.

Investigation on the tribological performance of functionalized nanoscale silica as an amphiphilic lubricant additive

In order to enhance tribological performance of both water-based and oil-based lubricant, the SiO2 nanoscale ionic liquid (NIL), an amphiphilic lubricant additive, was prepared by using a sulfuric acid terminated organo-silane as corona and polyether amine as canopy. Various analytical techniques were used to characterize the SiO2 NIL and stability of the nanolubricants. A ball-on-disk tribometer was adopted to investigate the lubrication enhancement of the SiO2 NIL in both water-based and oil-based lubricants. The results show that the SiO2 NIL can reduce the coefficient of friction (COF) and wear in these two lubricant groups, especially in the water-based lubricant. The lubrication mechanisms are ascribed to the polishing, ball bearing and mending effects of the SiO2 NIL.

Intraurethral lidocaine use during urodynamics in female patients: A systematic review and meta-analysis.

Pain and discomfort may occur in catheterization during a urodynamic examination. A lidocaine gel combined with a water-based lubricant is sometimes used to reduce pain during catheterization. Several studies claimed that intraurethral lidocaine administration could cause inaccurate urodynamic parameters results. However, its definite effects in urodynamics testing on humans are still not clear. We aimed to evaluate the effects of intraurethral lidocaine on pain and urodynamic study parameters in patients undergoing an invasive urodynamic examination. A systematic search adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol was performed in the MEDLINE, PubMed, and ScienceDirect databases for randomized controlled trials (RCTs). The bias of the studies is evaluated using the Cochrane risk of bias tool by two independent reviewers. The analyses of continuous outcomes were displayed as mean difference (MD), whereas odds ratio is used to analyze dichotomous data. Heterogeneity between studies is determined using the I2 value. A total of three RCTs out of 622 discovered that articles were eligible for analysis. Forest plot analysis of the mean visual analogue scale difference of the studies indicated an insignificant difference between the lidocaine and placebo group (MD -7.68; 95% CI -34.04 to -18.68, P ¼ .57). All urodynamic parameter results were also similar between the two groups (P > .05). Routine intraurethral lidocaine injection prior to a urodynamic study does not affect pain intensity and urodynamic parameters.

Water-Based Lubricants: Development, Properties, and Performances

Water-based lubricants (WBLs) have been at the forefront of recent research, due to the abundant availability of water at a low cost. However, in metallic tribo-systems, WBLs often exhibit poor performance compared to petroleum-based lubricants. Research and development indicate that nano-additives improve the lubrication performance of water. Some of these additives could be categorized as solid nanoparticles, ionic liquids, and bio-based oils. These additives improve the tribological properties and help to reduce friction, wear, and corrosion. This review explored different water-based lubricant additives and summarized their properties and performances. Viscosity, density, wettability, and solubility are discussed to determine the viability of using water-based nano-lubricants compared to petroleum-based lubricants for reducing friction and wear in machining. Water-based liquid lubricants also have environmental benefits over petroleum-based lubricants. Further research is needed to understand and optimize water-based lubrication for tribological systems completely.

A comparison of tribological properties of nanolubricants containing carbon nanotori and additional additives

This work presents the effects of five inorganic nanoparticles as additives, i.e., CNp (carbon nanotori particles), TiO2, MoS2, MoO3, and HcNT (halloysite clay nanotubes), in three different lubricants (oil-based, grease, and water-based). Nanolubricants were prepared by adding 1 wt% particles into each type of lubricant. Tribological properties of nanolubricants were determined and compared under anti-wear (AW) and extreme pressure (EP) conditions. CNp showed a decrease in coefficient of friction (COF) by 22% when added to water-based lubricant. Additionally, CNp demonstrated an improvement in limiting pressure of seizure (poz) of 74%, 52%, and 1621% for oil-based lubricant, grease, and water-based lubricant, respectively. Comparing 1 wt% CNp added to water-based lubricant with oil-based lubricant and grease, the improvements become outstanding under EP conditions. An increase in poz by 2479% compared to oil-based lubricant, and 789% compared to grease, was observed. In addition, a decrease of 66–69% in average wear scar diameter (AWSD) was obtained in comparison to oil-based lubricant and grease. Tribological mechanisms of carbon nanotori provide a rolling/sliding effect under AW conditions, and a load-bearing effect under EP conditions.

Thermo-mechanical forging of 708M40 steel ring samples: experiments and modelling

A series of ring compression tests using BS970:708M40 alloy steel samples were studied. These tests were conducted using a 2-factor soak-temperature variable, namely 1030 °C and 1300 °C, and a 4-factor lubricant variable consisting of unlubricated samples, synthetic water-based, graphite water-based, and graphite and molybdenum disulphide viscous grease. The lubricant agents were all applied to the tool/billet interface. Process variables such as blow force and heating were controlled with the use of a gravitationally operated drop hammer and an automated programmable induction-heating unit. This matrix of the experimental parameters offered a sound base for exploring dominant factors impacting upon bulk deformation. This deformation was measured using fully calibrated equipment and then systematically recorded. A finite element modelling framework was developed to further improve the thermo-mechanical deformation process understanding, with finite element (FE) predictions validated through experimental measurement. Through the combined experimental and FE work, it was shown that temperature variation in the experimental parameter matrix played a larger role in determining deformation than the lubrication agent. Additionally, the use of synthetic and graphite water-based lubricants does not necessarily produce greater deformation when used in high-temperature forgings due to the lubricants breaking down, evaporating, or inducing rapid billet cooling as a result of the carrier used (water). Graphite-molybdenum disulphate grease far outperforms the other lubricants used in this trial in reducing friction and allowing deformation to occur across a die-face.

Ultralow friction of copper by a green water-based lubricant containing phytic acid

Water can be used as an ecological lubricant base if the water-based lubricant additives are properly developed to enhance its tribological properties. Moreover, those additives should be friendly to both human and nature. Inositol hexakisphosphoric acid (IP6), known as phytic acid, is biodegradable and non-toxic and widely used in food industrial. We focus here on understanding the lubrication of copper by IP6 aqueous solution. A pin-on-disk tester is used to investigate the lubrication performance of using IP6 aqueous solution under boundary lubrication condition. Lower friction coefficient of 0.03 is obtained when 20 wt% IP6 solution is used. The tribofilms are characterized by using X-ray photoelectron spectroscopy. The results indicate that the surface hydrate tribofilms from adsorption of IP6 molecules on the copper surface provides excellent lubrication performance.

Topical estrogen, testosterone, and vaginal dilator in the prevention of vaginal stenosis after radiotherapy in women with cervical cancer: a randomized clinical trial

BackgroundWe aimed to evaluate the effects of different therapeutic options to prevent the evolution of vaginal stenosis after pelvic radiotherapy in women with cervical cancer.Methodsopen-label randomized clinical trial of 195 women, stage I-IIIB, aged 18–75 years, using topical estrogen (66), topical testosterone (34), water-based intimate lubricant gel (66), and vaginal dilators (29) to assess the incidence and severity of vaginal stenosis after radiotherapy at UNICAMP-Brazil, from January/2013 to May/2018. The main outcome measure was vaginal stenosis assessed using the Common Terminology Criteria for Adverse Events (CTCAE) scale and percental changes in vaginal volume. The women were evaluated at four different times: shortly after the end of radiotherapy, and four, eight, and 12 months after the beginning of the intervention. Statistical analysis was carried out using Symmetry test, Kruskal-Wallis test and multiple regression.Resultsthe mean age of women was 46.78 (±13.01) years, 61,03% were premenopausal and 73,84% had stage IIB-IIIB tumors. The mean reduction in vaginal volume in the total group was 25.47%, with similar worsening in the four treatment groups with no statistical difference throughout the intervention period. There was worsening of vaginal stenosis evaluated by CTCAE scale after 1 year in all groups (p < 0.01), except for the users of vaginal dilator (p = 0.37).Conclusionsthere was a reduction in vaginal volume in all treatment groups analyzed, with no significant difference between them. However, women who used vaginal dilators had a lower frequency and severity of vaginal stenosis assessed by the CTCAE scale after one year of treatment.Trial registrationBrazilian Registry of Clinical Trials, RBR-23w5fv. Registered 10 January 2017 - Retrospectively registered.

Lubrication and Anti-Rust Properties of Jeffamine-Triazole Derivative as Water-Based Lubricant Additive

With the worldwide concern of environmental protection, water-based lubricants exhibit extensive potential applications due to their advantages of energy-conservation, innocuity, and competitive price. Nonetheless, the common lubricating additives currently available in the market are mainly oil-based, while multifunctional water lubricants are rare. This paper reports a sulfur- and phosphorus-free multifunctional additive with high water-solubility, which is applicable for multitype material surfaces. Specifically, through the Mannich reaction method, a Jeffamine-triazole derivative was synthesized from olyetheramine and benzotriazole. Compared with distilled water, the derivative exhibited superior friction reduction and wear resistance properties in water, with the friction reduction rate up to 72.7% and 70.2% for steel/steel and steel/aluminum contacts, respectively, when the concentration of the JD2000 is 2 wt.%. Remarkably, the wear resistance property for steel/aluminum contact is improved by 88.2%. Moreover, the additive showed corrosion inhibition on the metal surface by 75.5%. We further revealed the lubrication and anti-rust mechanisms: the additives are adsorbed on the surfaces through nitrogen atoms, and the long-chain structure of polyether can cover the sliding surfaces, forming a stable viscoelastic film to prevent the severe damages caused by the direct contact between rough friction pairs. Concurrently, the dense protective film can resist the corrosion of environmental media on the metal surface and delay the metal rust. This research may provide a candidate for an ecofriendly multifunctional water-based lubricating additive.

Super Low Friction Characteristics Initiated by Running-in Process in Water-based Lubricant for Ti-Alloy

Super Low Friction Characteristics Initiated by Running-in Process in Water-based Lubricant for Ti-Alloy

Roughness-dependent tribological characteristics of water-based GO suspensions with ZrO2 and TiO2 nanoparticles as additives

Hybrid nanosuspensions were synthesised through ultrasonically dispersing ZrO2 or TiO2 nanoparticles into graphene oxide (GO) nanosheet solutions for water-based lubrication. The effect of contact pair roughness on the tribological behaviours of the ZrO2/GO and TiO2/GO hybrid nanosuspensions were investigated using a block-on-ring testing approach. With a relatively smooth ring, the use of the nanosuspensions could reduce abrasive wear, and hence improve worn surface quality, owing to the relieved asperity ploughing. With a ring of moderate roughness, the use of the nanosuspensions suppressed the occurrence of adhesive wear through relieving the effect of asperity contact. With a relatively rough ring, the nanosuspensions generated a deposited layer of hybrid nanoparticles at the contact area that can prevent surface asperities from direct contact, thus leading to lower adhesive wear and friction.

Carbon Nanotori Structures for Thermal Transport Applications on Lubricants.

Carbon nanostructures have been recently applied to improve industrial manufacturing processes and other materials; such is the case for lubricants used in the metal-mechanic industry. Nanotori are toroidal carbon nanostructures, obtained from chemical treatment of multi-wall carbon nanotubes (MWCNTs). This material has been shown to have superb anti-wear and friction reduction performance, having the ability to homogeneously disperse within water in concentrations between 1–2 wt.%. Obtained results of these novel nanostructures under water mixtures and novel additives were a set point to our studies in different industrial lubricants. In the present work, nanotori structures have been applied in various filler fractions as reinforcement to evaluate the behavior in thermal transport of water-based (WB) and oil-based (OB) lubricants. Temperature-dependent experiments to evaluate the thermal conductivity were performed using a thermal water bath ranging from room temperature up to 323 K. The obtained results showed a highly effective and favorable improvement in the heat transport of both lubricants; oil-based results were better than water-based results, with nanotori structures increasing the lubricants’ thermal transport properties by 70%, compared to pure lubricant.