Lubrication System Research Articles

Compaction of Hydrophobic Molybdenum Disulfide Coatings for Promoting Tribological Behaviors on Engineering Steel

Ambient environment has a crucial effect on the lubrication performance of molybdenum disulfide (MoS2) coatings. In this work, we fabricated porous MoS2 coatings via a facile optimized aerosol-assisted chemical vapor deposition (AACVD) method. It is found that the obtained MoS2 coating demonstrates outstanding antifriction and antiwear lubrication performance with the coefficient of friction (COF) and wear rate as low as 0.035 and 3.4 × 10–7 mm3/Nm in lower humidity (15 ± 5)%, respectively, which is comparable to the lubrication ability of pure MoS2 in vacuum. In addition, the hydrophobic property of porous MoS2 coatings is suitable for infusing lubrication oil to achieve stable solid–liquid lubrication in higher humidity (85 ± 2)%. The composite lubrication system shows excellent tribological behavior in both dry and wet environments, which will alleviate the sensitivity of the MoS2 coating to the environment and ensure the service life of the engineering steel in complex industrial backgrounds.

Modelling and Experimental Study of Power Losses in Toothed Wheels

In recent decades, the request for more efficient performances in the aeronautical sector moved researchers to pay particular attention to all the related mechanisms and systems, especially with respect to the saving of power. In this context, the bearing modeling and design, as well as gear coupling, play a fundamental role. Moreover, the need for low power losses also concerns the study and the implementation of advanced lubrication systems, especially for high peripheral speed. With the previous aims, this paper presents a new validated model for toothed gears, added to a bearing model; with the link of these different submodels, the whole model describes the system’s dynamic behavior, taking into account the different kinds of power losses (windage losses, fluid dynamic losses, etc.) generated by the mechanical system parts (especially rolling bearings and gears). As the bearing model, the proposed model is characterized by high numerical efficiency and allows the investigation of different rolling bearings and gears with different lubrication conditions and frictions. A comparison between the experimental and simulated results is also presented in this paper. The analysis of the results is encouraging and shows a good agreement between experiments and model simulations, with particular attention to the power losses in the bearing and gears.

Comparative Cutting Fluid Study on Optimum Grinding Parameters of Ti-6Al-4V Alloy Using Flood, Minimum Quantity Lubrication (MQL), and Nanofluid MQL (NMQL)

Titanium alloys have been of paramount interest to the aerospace industry due to their attractive characteristics. However, these alloys are difficult to machine and require grinding post-processes for quality assurance of the products. Conventional grinding takes a long time and uses a flood coolant-lubrication technique, which is not cost effective nor environmentally friendly. Several studies have been performed to prove the viability and benefit of using Minimum Quantity Lubrication (MQL) with vegetable or synthetic-ester fluids. This work aims to find the optimum grinding parameters of creep feed grinding Ti-6Al-4V with a green silicon carbide wheel, using a flood lubrication system with water-soluble synthetic oil, MQL with ester oil, and nano-MQL (NMQL) using alumina-nanopowder homogeneously dispersed within an ester oil. It is concluded that at 0.635 mm and 1.27 mm infeeds, the three lubrication methods performed similarly. At an infeed of 1.905 mm, MQL did not provide desirable quality, though NMQL and flood lubrication performed practically identically. At a cross feed of 0.254 mm, an infeed of 1.27 mm, and a table feed rate of 6.7 m/min, these grinding parameters provide a material removal rate of 2163 mm3/min with a surface roughness across (Ra) of 0.515 µm. These parameters provide the quickest material removal rate while still maintaining industrial quality. This conclusion is based on environmental, economic, and qualitative results.

Achieving Greener, Super-Robust Performance Water-Based Lubrication: Obtained by a Multifunctional Ionic Liquid Aqueous System and Formation of Unique Interfacial Interactions

Owing to the green, high-performance, and application-specific work conditions, water-based lubricating systems show unlimited potential for chemical engineering development. The interfacial behavior of functional additives in aqueous systems is complex and variable due to polarity and interfacial activity, thus showing important research significance. Herein, five novel ionic liquids were synthesized; their unique interfacial behavior in the polar water system contributes a lot to the advanced corrosion resistance and the improved extreme pressure-bearing capacity. The polar groups in the molecular structure of ionic liquids can adsorb preferentially in competition with water molecules, resulting in the formation of an adsorption layer with a high elastic modulus on the metal surface. Benefiting from the tribochemical reaction and the strong polar adsorption effect, the tribofilm at the sliding asperity exhibited effective antiscuffing and antiwear performance. Moreover, their characteristic cationic groups enrich the driving force of the molecular self-assembly process and enhance the ability to form ordered molecular aggregates, whose behavior in an aqueous system facilitates super-robust lubricity. This work can promote the in-depth understanding, future design, and optimization of the aqueous lubricating system, providing content enrichment and expansion for the lubrication technology for harsh service conditions.

Application of DFT and TD-DFT on Langmuir Adsorption of Nitrogen and Sulfur Heterocycle Dopants on an Aluminum Surface Decorated with Magnesium and Silicon

In this study, we investigated the abilities of nitrogen and sulfur heterocyclic carbenes of benzotriazole, 2-mercaptobenzothiazole, 8-hydroxyquinoline, and 3-amino-1,2,4-triazole-5-thiol regarding adsorption on an Al-Mg-Si alloy toward corrosion inhibition of the surface. Al-Si(14), Al-Si(19), and Al-Si(21) in the Al-Mg-Si alloy surface with the highest fluctuation in the shielding tensors of the “NMR” spectrum generated by intra-atomic interaction directed us to the most influence in the neighbor atoms generated by interatomic reactions of N → Al, O → Al, and S → Al through the coating and adsorbing process of Langmuir adsorption. The values of various thermodynamic properties and dipole moments of benzotriazole, 2-mercaptobenzothiazole, 8-hydroxyquinoline, and 3-amino-1,2,4-triazole-5-thiol adsorbed on the Al-Mg-Si increased by enhancing the molecular weight of these compounds as well as the charge distribution between organic compounds (electron donor) and the alloy surface (electron acceptor). Finally, this research can build up our knowledge of the electronic structure, relative stability, and surface bonding of various metal alloy surfaces, metal-doped alloy nanosheets, and other dependent mechanisms such as heterogeneous catalysis, friction lubrication, and biological systems.

Varnish Formation and Removal in Lubrication Systems: A Review.

This study presents the current literature regarding the investigation of varnish contamination among the various types of lubricant contaminations. As the duration of use of lubricants increases, the lubricant deteriorates and may become contaminated. Varnish has been known to cause filter plugging, sticking of the hydraulic valves and fuel injection pumps, flow obstruction, clearance reduction, poor heating and cooling performance, and increased friction and wear in various lubrication systems. These problems may also result in mechanical system failures, performance degradation, and increased maintenance and repair costs. To improve the problems caused by varnish contamination, an adequate understanding of varnish is required. Therefore, in this review, the definitions and characteristics, generating machinery, generating mechanisms, causes, measurement methods, and prevention or removal methods of varnish are summarized. Most of the data presented herein are reports from manufacturers related to lubricants and machine maintenance that are included in published works. We expect that this summary will be helpful to those who are engaged in reducing or preventing varnish-related problems.

Hysteresis in three-dimensional multi-layer molecularly thin-film lubrication

Abstract For three-dimensional multi-layer molecularly thin-film lubrication system with elastic substrates, roles of hysteresis on tribological properties are investigated by using the multiscale simulation method. It is found that multiple stick-slip transitions with/without hysteresis loops appear in a sliding process and form a quasi-periodic progress with lattice distance. For the few-/multi-layer thin-film lubrication system, as the load increases, the hysteresis length monotonously increases/tends to keep constant. The hysteresis is mainly caused by the relaxation of metastable states of solid atoms in the elastic substrates, which delays the system back to its equilibrium states. In the quasi-periodic shearing progress, the effective elastic coefficients and the hysteresis lengths approximately remain unchanged, which reveals that although the hysteresis loops with the same lengths appear in the sliding process, the total systematic energy is still conserved. These findings not only provide a profound understanding of roles of hysteresis in the thin-film lubrication system but also show the effects of film layers and loads on the systematic tribological properties, which are of great significance for practical applications.

Novel concept of nano-additive design: PTFE@silica Janus nanoparticles for water lubrication

Polytetrafluoroethylene (PTFE) has been widely used as a lubrication additive for reducing friction and wear; however, the hydrophobic nature of PTFE restricts its application in eco-friendly water-based lubrication systems. In this study, for the first time, we designed novel PTFE@silica Janus nanoparticles (JNs) to meet the requirement for additives in water-based lubricants, which have excellent dispersion stability in water attributed to the unique amphiphilic structure. By introducing the lubrication of the aqueous dispersion of the JNs with a concentration of 0.5 wt%, the coefficient of friction (COF) and wear volume were reduced by 63.8% and 94.2%, respectively, comparing to those with the lubrication of pure water. Meanwhile, the JNs suspension also exhibits better lubrication and wear-resistance performances comparing to commercial silica and PTFE suspensions. The excellent tribological behaviors of PTFE@silica JNs as nano-additives could be attributed to the synergetic effect of the two components, where the PTFE provided lubrication through the formed tribofilms on the friction pairs, and the rigid silica further enhanced the wear-resistance performance. Most importantly, the unique structure of JNs makes it possible to use PTFE as an additive in water-lubrication systems. Our study shed light on the design and application of novel JNs nanomaterials as additives to meet the requirements of future industrial applications.

Multi-Response Optimization of Milling Process of Hardened S50C Steel Using SVM-GA Based Method

This study aims to find the optimized parameters for surveying the milling process of S50C steel in a minimum quantity lubrication (MQL) environment using a support vector machine-genetic algorithm (SVM-GA). Based on the experimental matrix designed by the Taguchi method, surface roughness and cutting force data were collected corresponding to each experiment with changes in input parameters such as cutting speed, tooth feed rate, and axial depth of cut, along with changes in two parameters of the minimum lubrication system: flow rates and injection pressure. Through analysis by the SVR-NSGAII method, the study obtained the optimal parameters of cutting and lubricating conditions when prioritizing either surface roughness or focusing on the cutting force; however, the most comprehensive result is believed to be achieved by balancing these two factors. So, when striving for the neutral value of both output parameters, which are surface roughness (µm) and cutting force (N), the optimum parameters including injection pressure (MPa), flow rates (mL/h), cutting speed (m/min), feed rate (mm/tooth), and axial depth of cut (mm) are proposed.

Graphitic carbon nitride quantum dots as novel and efficient friction-reduction and anti-wear additives for water-based lubrication

Undeniably, advances in water-based nano-additives play a considerable role in energy conservation and pollution reduction accompanied by the resurgence of water-based lubricants. Graphitic carbon nitride quantum dots (g-CNQDs) have attracted remarkable attention in water-based lubricant additives owing to their strong designability, favorable mechanical property, and unique self-lubricating effect. Therefore, a series of different-sized g-CNQDs with good water dispersibility were expediently synthesized via a hydrothermal strategy and directly used as water-based lubricant additives. Tribological tests indicated that the tribological behaviors of the g-CNQDs-based additives displayed an obvious phenomenon of performance-dependent physical dimensions. With the introduction of g-CNQDs-based additives (1.0 wt%) into the water-based lubrication system, which friction-reduction, anti-wear, and load-supporting performances can be maximally increased by 45.5%, 94.0%, and 233.3%, respectively. Meanwhile, the long-term operating performance of the lubrication system can be promoted under high-load conditions. The formed tribo-film caused by tribo-chemical reaction integrated with the nano-lubrication effect of g-CNQDs collectively contributed to their good tribological performances.

ГРУППОВАЯ СИСТЕМА СМАЗКИ ЭКСКАВАТОРА ЭШ ЛУБРИКАТОРОМ С ПНЕВМАТИЧЕСКИМ ПРИВОДОМ

A group lubrication system of mechanical components for a walking excavator is proposed, the original design of a lubricator with a pneumatic drive and a controlled electro-magnetic valve is developed

СИСТЕМА СМАЗКИ ЭКСКАВАТОРА ЭШ 20-90 ЛУБРИКАТОРОМ С ПРУЖИННЫМ ПРИВОДОМ

An automated lubrication system of mechanical components for a walking exca-vator is proposed, an original lubricator design with a spring drive and a controlled shut-off valve is developed

A Novel Method for the Numerical Investigation of Pendulum Slider Pumps

Inadequate lubrication might lead to high friction and wear and can ultimately translate in a higher dissipation of energy, initiation and propagation of fracture and material fatigue. These occurrences are avoided or delayed thanks to an efficient lubricating system. The core of a reliable system is the hydraulic pump which, in the automotive field, is also responsible for power transmission and cooling. Given the importance of such components, improving reliability and performance of the pumps is a topic that is greatly pursued by manufacturers. A machine that is infrequently addressed in the open literature of the fluid power field is the pendulum slider pump. This kind of machine has the makings of high durability performance, short response time, and significant ability to withstand flow contamination by solid particles. Considering the available literature, no Computational Fluid Dynamics (CFD) studies have been presented so far. Among the complexities that hindered the application of CFD to this machine, motion complexity and narrow gaps make the development of a numerical algorithm for its modelling non-straightforward. In this work, the authors present the development and the application of a CFD model for the simulation of pendulum slider pumps. The structured mesh generation process has been successfully applied to a state-of-the-art pendulum slider pump for automotive applications, and the outcome of the numerical investigation has been validated against an on-purpose built test bench. The results both in terms of variable displacement and fixed displacement behaviour are shown. This work proofs the suitability of the developed model for the analysis of hydraulic pendulum slider pumps.

Method for assessing the anti-carbon properties of unmanned aerial vehicle engines

At present, the process of design and production of unmanned aerial vehicles has been making progress in Russia, which is caused by the relatively low cost, small size, absence of life hazard to a pilot, stealth, self-sustainability, mobility compared to manned aircraft. At the same time, two-stroke gasoline engines, possessing a higher power-to-volume ratio, unsophisticated design, and lower production costs in comparison with four-stroke gasoline engines, have become widely used in these aircraft. These engines lack a conventional lubrication system, so the oil is supplied to lubricate the cylinder-piston group in the form of a fuel-oil mixture, which burns during the operating procedure together with the fuel. In this case, high-temperature deposits such as carbon and lacquer are accumulated on the parts of the cylinder-piston group. The formation of carbon reduces the engine power, its service life and efficiency, causes an increase in operating costs. One of the solutions to this problem is the use of motor oils with a high level of anti-carbon properties. However, currently a method for assessing the anti-carbon oil properties for unmanned aerial vehicle engines is not available. In accordance with the described chemmotological process, the method was developed, the test equipment (Panel Coking Test Apparatus) was selected and the test modes were established (plate temperature – 290°C, oil temperature in the crankcase – 100°C, spray speed – 800 rev/min, test time – 4 h), allowing you to evaluate and rank motor oils for unmanned aircraft engines based on the anti-carbon properties in the laboratory. As tested, Motul Kart Grand Prix 2T oil has the least tendency for carbonization among tested motor oil samples. Laboratory and bench tests of Novoyl-DD and Motul Kart Grand Prix 2T oils show a high degree of convergence.

Failure Analysis of Induced Draft Fan Bearing in PT Semen Padang Using The RCM Method

The development of the technology is getting trigger competition in industri. To compete, companies should can provide products and the quality of services best for consumer. This study aims to find out the causes of bearings that are damaged in the Induced Draft Fan (IDF Bearing) and how to plan strategic maintenance of IDF Bearing. The method used is reliability centered maintenance (RCM). The causes of bearing damage are analyzed using the Failure Mode Effect and Critical Analysis (FMECA) method. The results of this study show that the cause of IDF Bearing damage is clearance with an RPN value of 210, lubrication system with an RPN value of 36, unbalance with an RPN value of 72, and high temperature with an RPN value of 54. Scheduled Restoration Maintenance is applied for IDF Bearing , where task or preventive maintenance in the form of oil change with a time of 5803.2 hours or 241 days.

Tribological Performance of Gd-DLC and Eu-DLC Coatings in the Presence of Synthetic Oils Containing Ionic Liquid Additives

The lubrication of gadolinium-doped diamond-like carbon (Gd-DLC) and europium-doped diamond-like carbon (Eu-DLC) coatings with trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate ([P66614][DEHP]) ionic liquid (IL) as 1 wt% additive in polyalphaolefin (PAO) 8 was studied. The results of the friction tests under boundary lubrication conditions showed that Gd-DLC and Eu-DLC coatings in the presence of the IL exhibit a friction reduction, especially with the high atomic concentration of doped metal. Later, the surface observation after the long-term wear test indicated that Gd-DLC coatings have less abrasive wear and higher anti-wear properties compared to Eu-DLC coatings due to the enhanced formation of tribofilms derived from the phosphorus of the IL on the steel ball as the counter body. From these results, we have concluded that the friction reduction and the anti-wear property in the presence of the IL can be improved by changing the type and the concentration of the doped metals. This clearly shows that the novel lubrication system combining the Gd-DLC and Eu-DLC coatings with the IL allows for guiding future research and development.Graphical abstract

Two-step printing Ni3Al/Cr3C2-Ti3SiC2/MoS2 composite films using electrohydrodynamic atomization with a biomimetic shark-skin mask

Natural structures with outstanding tribological properties have inspired mankind to imitate their designs, and the purpose is to minimize friction and wear. Herein, in consideration of the exceptional high-temperature strength and wear resistance of Cr3C2 reinforced Ni3Al matrix composite, Ni3Al/Cr3C2 convex texture was printed through the usage of electrohydrodynamic atomization (EHDA) technology, with a mask that simulated bioinspired sharkskin. Furthermore, the corresponding synergistic lubrication behavior between the convex texture and Ti3SiC2/MoS2 lubricants was explored. Experimental results indicated that the composite films consisting of inspired-sharkskin Ni3Al/Cr3C2 convex texture and Ti3SiC2/MoS2 lubricants exhibited favorable adhesive strength, giving long wear life and excellent stability in friction. This was mainly ascribed to the convex textured enhanced surface wettability of the polished substrate. The composite films performed a favorable friction coefficient of 0.17 at ambient temperature, which was decreased by 70.2 % and 39.3 %, with respect to the structure-less Ni3Al/Cr3C2 and Ti3SiC2/MoS2 composite films, respectively. This improvement could be explained by the sharkskin convex texture served as a reservoir for storing lubricants and supported to form more continuous transfer films. In this work, an efficient and potential approach was proposed for exploiting lubrication structures in future interfacial engineering and lubrication systems under peculiar service environments.

Assessment of geometrical dimensions and puncture feasibility of microneedles manufactured by micromilling

Microneedles are an emerging technology designed to deliver drugs into human tissue. In this work, we assess the microneedle’s manufacturability by employing micromilling with a minimum quantity lubrication (MQL) system. A set of AISI 316L square pyramidal microneedles was fabricated and characterized using dimensional and surface metrology. Needle height (Hn), base length (Lb), tip radius (Rt), and the tip’s angle (θ) were studied. Additionally, surface roughness was quantified to correlate surface topography damage with tool wear (Dr). Experimental data shows tip truncation after manufacturing 30 needles (i.e., a tip radius between ~32 μm and 49 μm for manufacturing 10 and 30 needles, respectively). Additionally, to evaluate the effect of the tip’s morphology on the proficiency of the microneedles for a puncture, a numerical analysis to study the impact of tip truncation length (Tt) on puncture with an in silico assessment using COMSOL Multiphysics was performed. Data and insights from this work suggest that micromilling microneedle arrays is viable, considering the number of needles machined according to the cutting parameters selected to ensure functionality.

Development and potential use of MWCNT suspended in vegetable oil as a cutting fluid in machining of Monel 400

The heat dissipation problem that arises when machining difficult to cut materials can be mitigated by using nano-cutting fluids, which have a much higher thermal conductivity value than the basic lubricants. Since the heat carrying capacity of the Minimum Quantity Lubrication (MQL) system is significantly lower than that of other coolants, a number of nano-additives are used to increase its cooling effectiveness. Therefore, this study firstly focuses on the assessment of nano-cutting fluids and theirsignificant efficacy in the machining operation of nickel-based alloys. Multi-walled carbon nanotube (MWCNT) suspended in vegetable oil is compared with distinct cooling environmental conditions namely, dry, MQL and cryogenic carbon dioxide (CO2). The novelty of this work is that the different volume fractions of 0.2 – 1 wt% of MWCNT were dispersed to study the contact angle, viscosity and thermal conductivity of the prepared molecular liquid and then, the potential of MWCNT suspended in vegetable oil is used to evaluate the outcomes of surface roughness (Ra), cutting temperature (CT) and tool wear (Vb) while machining Monel 400 alloy. The outcomes affirmed that employing nano MQL in machining operations resulted in a mean reduction of about 65% in the temperature evolved concerning no coolant condition. Additionally, the use of nanoparticles leads to an improved surface finish and abridged tool wear.

Synthesis of polyzwitterionic carbon dots with superior friction and fatigue control behaviors under water lubrication

Water lubrication is indispensable for industrial domains, meaning that the tribological behaviors of water are essential for practical applications and should be improved. Herein, a class of zwitterionic polyethyleneimine-grafted carbon dots (CDs-ZPEI0.6-10k) were rationally conceived and synthesized by the facile ring-opening reaction between 1,3-propanesultone (PS) and the PEI0.6-10k skeletons onto CDs-PEI0.6-10k. The intrinsic hydration effect of zwitterionic groups endowed the CDs-ZPEI0.6-10k with superior dispersibility and lubricity in water. The tribological results confirmed that the CDs-ZPEI10k with copious hydration and adsorption sites not only maximally reduced the wear rate and friction coefficient for water by 66.1 % and 72.5 % but also performed steadily under harsh conditions, which benefited from the strong hydration lubrication and ball-bearing function of CDs-ZPEI10k. The worn surface analyses evidenced that the CDs-ZPEI10k could be compacted into a uniform tribofilm with a thickness of about 320 nm to reduce friction while restraining the fatigue damage on the rubbing steel surfaces. Undoubtedly, the hydration, adsorption, and deposition synergistically induce the excellent tribological performances of CDs-ZPEI10k. This study proposed a feasible strategy for designing and synthesizing polyzwitterionic CDs, enabling a high-efficiency aqueous lubrication system with robust friction and fatigue control behaviors.