Lubricant Materials Research Articles

Modelling of the Process of the Friction Couple Contacting and Examining the Conditions of Forming an Adsorbating Monolayer on the Friction Surface Regarding the Use of a Lubricant Material

The processes of friction and wear heavily depend on the structural formation of a block, the choice of the wear-resistant substances and effective lubricant material s for them, as well as the operational conditions for the machinery. The contacting of two elastic solids, under high (p_cp>200 MPa) normal contact and shear pressure, regarding the presence of a lubricant material in the place of contact is of our special interest. Nowadays one of the most common and effective ways of achieving reliability and a longer life cycle of the contacting machine elements and machines is the use of a lubricant material. In the course of developing new lubricant material and anti-friction substances and examining the properties of the existing materials one should pay special attention to the tribological trial plants to specify the requirements and recommendations for the producers of the substances regarding the technology of their future use. That’s why, the laboratory experiments, aimed at a detailed research of the influence of the lubricant material supply on the change of the parameters at the friction contact are timely. The current paper explores the influence of modes of the lubricant material supply on the change of the triboloical parameters of the friction couple contact and its durability with the help of the method of physical modelling of the contact of a heavily loaded friction couple. It also studies the conditions of forming a resistant coating on the friction surfaces that prevents from the abrasive wear of their surface layers.

Performance improvement in rolling of hot-rolled wide strip by supplying lubricant to the backup rolls of a finishing

Some well-known methods for increasing effectiveness in wide strip hot rolling were analyzed in the presented work. It was performed the evaluation of dependence of lubricant materials on wear of rolls. By means of the device “multiple regression” it was obtained regressive dependence and the coefficient of changing linear sizes of working rolls for hot rolling mill – “2000”. The methods of volume consumption parameters definition were improved on the base of carried out researches. The recommendations were offered concerning assignment of lubricant consumption with taking into consideration the changes of linear sizes of rolls.

An investigation of cutting forces and tool wear in turning of Haynes 282

Superalloys belong to the group known as difficult to cut materials, and inside this category of material Haynes 282 is considered a novel material with huge applicability subjected to automobile, aerospace and gas turbine industries. The characterization of machining of this new material evidences a lot of importance. Therefore, this paper presents an experimental investigation into the effect of lubricant pressure and material heat treatment on cutting forces, machined surface quality and tool wear evolution on turning of superalloy Haynes 282. Face turning of hollow discs with fixed cutting conditions with cemented carbides tools where carried out to evaluate machinability.The results show that Haynes 282 Alloy in solution annealing Large Grain Solution (LGS) state has better machinability than precipitation hardened Large Grain Aged (LGA) state in terms of force levels and tool wear. In terms of coolant pressure effect, a significant improvement is not observed in the case of High pressure coolant (HiPC).

Intelligent Solid Lubricant Materials with Failure Early-Warning Based on Triboluminescence

In this work, triboluminescent powders (SrAl2O4: Eu2+, Dy3+) were composited with the typical graphite/epoxy solid lubricant materials, and the corresponding tribological properties and triboluminescent performance were investigated. The results suggest that the introduction of SrAl2O4: Eu2+, Dy3+ could not only maintain the friction coefficient and the wear rate of the graphite/epoxy solid lubricant materials, but also endow the composites intense triboluminescence. Based on the above results, a bilayered SrAl2O4: Eu2+, Dy3+/graphite/epoxy self-lubricating bulk material and a bilayered SrAl2O4: Eu2+, Dy3+/graphite/epoxy solid lubricant coating were developed, and the intelligent wear out early-warning was in situ achieved in the lubricant coating based on the monitoring of triboluminescence.

Investigation of the microstructural, surface and optical properties of nano-layer MoxSy thin film deposited by thermionic vacuum arc

Molybdenum disulfide (MoxSy) thin film was deposited onto the glass substrate using Thermionic Vacuum Arc (TVA) technique. MoS2 as know as low-friction coefficient and solid lubricant material and it is a 2-dimension material. In this study, properties of the 2D (MoxSy) were determined. In 2D coating, mixed phase of MoS2, Mo2S3, Mo3S4 and Mo15S19 crystal reflection planes were detected in XRD pattern. The thickness of the film was measured as to be 30 nm. The crystallite sizes were calculated in the range of 6–20 nm. Refractive index value of the deposited layer was found nearly 2. The band gap value of the deposited 2D layer is nearly equal to about 1.98 eV. The dielectric constant for the deposited layer is very close to 4.3. To determine the optical impurity and defects, photoluminescence and Raman analyses were done. Also, friction coefficient of the 2D nano layer was measured by ball on disk technique.

Macroscale Superlubricity Enabled by the Synergy Effect of Graphene-Oxide Nanoflakes and Ethanediol.

Graphene has been recognized as an excellent lubrication material owing to its two-dimensional structure and weak interlayer interactions. However, most extant works concerning superlubricity involving graphene oxide have been limited to nanoscale or microscale dimensions (of the order of 1-10 μm). In present work, realization of a robust macroscale superlubricity state (μ = 0.0037), by taking advantage of the synergy effect of graphene-oxide nanoflakes (GONFs) and ethanediol (EDO) at Si3N4-SiO2 interfaces is reported. GONFs have been observed as being adsorbed on friction surfaces, thereby preventing direct contact between surface asperities. The extremely low shear stresses developed between these asperities contribute toward enhanced superlubricity and the resulting super-low wear. Meanwhile, the formation of partial-slip hydrodynamic boundary condition at the GONFs-EDO interface along with the formation of hydrated GONFs-EDO networks through hydrogen-bond interactions contribute to the generation of extremely low shear stresses of the liquid lubricating film. Such macroscale superlubricity provides a new approach toward realization of extremely low friction in GONFs through the synergy effect with liquids.

A STUDY ON ANTIWEAR PROPERTIES OF GRAPHENE WATER-BASED LUBRICANT AND ITS CONTACT WITH METALLIC MATERIALS

Due to their ecological and financial aspects, water-based lubricants may be competitive in use for production and sustainable technology. The paper presents tribological measurements results in the ball-flat friction node with reciprocal movement. The friction element manufactured of 316L stainless steel and 100Cr6 bearing steel cooperated under mixed friction with the use of water-based lubricants. Firstly, graphene flakes and graphite were applied as lubricant additives, both used as a similar reference material. Secondly, graphene lubricant reduced the friction coefficient and wear of friction elements. Interaction between water and graphene lubricants with 0.1 wt % and 1 wt % of graphene flakes and metal was also investigated. After 30 days of oxidation test in water and graphene lubricants, the Fe sample (Armco iron) surface was covered in graphene flakes with iron oxide structures. A compact coverage of the surface creates a protective layer against intensive oxidation in the distilled water-based graphene lubricant. The tests results have proven that the greater density of graphene flakes in the lubricant, the smaller is the amount of detected oxides. Graphene flakes agglomeration was observed in contact with the iron metal.

ExxonMobil may enter α-olefins business

ExxonMobil Chemical may enter the α-olefins market. The company is considering building a plant with about 350,000 metric tons per year of capacity in Baytown, Texas, where it recently opened an ethylene cracker. α-Olefins have seen strong demand in recent years as comonomers for linear-low-density polyethylene and as raw materials for detergents and lubricants. Additionally, ExxonMobil may build a 400,000-metric-ton-per-year plant for its Vistamaxx propylene-ethylene copolymers in Baytown. If the firm greenlights the plants next year, they will be set to open in 2021.

First-Principles Study of the Adsorption and Depolymerization Mechanisms of Sodium Silicate on Iron Surfaces at High Temperature

Silicate glasses are potential materials for lubrication at elevated temperature because of their exceptional thermal stability, low cost, and environmentally friendly properties. Although the frictional behaviors and characterizations of silicate glass tribofilms have been studied by a number of experiments, the formation mechanisms as well as the chemical insight into the iron–silicate tribofilm still remain unclear. In the present study, the adsorption and depolymerization of the sodium sorosilicate cluster Na6Si2O7 on a Fe(110) surface have been studied using both first-principles molecular dynamics and density functional theory. Comparisons of adsorption processes and electronic structure of some typical configurations at different temperatures have been carried out. The results strongly suggest that the silicate cluster chemically adsorbs on the Fe(110) surface by forming multiple Fe–nonbridging oxygen (NBO) bonds. The iron surface plays an important role in the dissociation of the NBO by significan...

Synthesis and characterization of copper foams through a powder metallurgy route using a compressible and lubricant space-holder material

In the present work, a compressible and lubricating space-holder material commonly known as “acrawax” was used to process Cu foams with various pore sizes and various porosities. The foams were processed without using binders to avoid contamination of their metal matrices. The lubricant space-holder material was found to facilitate more uniform flow and distribution of metal powder around the surface of the space holder. In addition, the use of acrawax as a space-holder material yielded considerably dense cell walls, which are an essential prerequisite for better material properties. The foams processed with a smaller-sized space holder were found to exhibit better electrical and mechanical properties than those processed with a coarser-sized space holder. The isotropic pore shape, uniform pore distribution throughout the metal matrix, and uniform cell wall thickness were found to enhance the properties pertaining to fine-pore foam samples. The processed foams exhibit properties similar to those of the foams processed through the lost-carbonate sintering process.

Improved wear resistance and mechanism of titanium aluminum based alloys reinforced by solid lubricant materials

Abrasion failure is a bottleneck problem that restricts the applications of titanium aluminum (TiAl) based alloys. This work has developed a facile method to endow TiAl alloys with superior wear resistance. TiAl composites reinforced by serpentine materials have been prepared by spark plasma sintering (SPS). Microstructural characterizations show that serpentine is well distributed in TiAl alloy matrix. Tribological behaviors in terms of a high-temperature friction and wear tester indicate that the reinforced particles play a positive role in decreasing wear rates and friction coefficients. Together with wear debris and high-temperature oxides, lubricant particles easily form a lubrication layer on frictional interfaces, which can help repair and compensate the worn-out pits and grooves thereby leading to the optimal wear resistance with the lowest friction coefficient of 0.41 and wear rate of 1.97 × 10−4 mm3/(Nm) at 400 °C–600 °C. This work sheds insights into evaluating the practicability of serpentine as a desirable solid lubricant and providing guidance for designing other serpentine-reinforced composites.

Modifying the lubricating and tribological properties via introducing the oleic acid in CuS nanomaterials for vehicle

Materials made from self-lubricating inorganic and organic composites have gained great attention due to advantages of the rust-resistance, light weight, low cost, and high compatibility. As a result, they have extensive applications in the friction and lubrication fields, typically for vehicle. With the help of the water bath and hydrothermal method, we have prepared the CuS nanomaterials with and without oleic acid modification. Various techniques, such as X-ray diffraction (XRD) spectra, transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS) and vertical universal friction as well as wear testing, have been employed to analyze the structure information and characterize the related tribological properties of our CuS nanomaterials. Results show that the morphologies of the CuS nanomaterials are nanorods. Increasing the surface area and the concentration of CuS nanorod additives can significantly reduce the friction coefficient and wear rate of pins in both unmodified and oleic acid-modified CuS nanomaterials. More than that, we find that when compared to those without oleic acid modification, the oleic acid modification enable the CuS nanomaterials to exhibit higher anti-wear properties. The EDS analysis shows that there is still a uniform tribo-film in the surface of oleic acid-modified CuS nanomaterials, implying the prominent tribological performances of CuS nanorods additives. Our results indicate that the Oleic acid-modified CuS nanorods can be served as a new lubricating and tribological material for vehicle.

Anomalous thermal stability in supergiant onion-like carbon fullerenes

Onion-like carbon fullerenes (OLCFs) are a promising material for applications in nanoscale devices, medicine, lubrication and superhard materials. Knowledge of the pyrolysis chemistry of OLCFs helps understanding the thermal-induced erosion of carbon-based resources and spacecraft materials. Here, using first-principle-based ReaxFF atomistic simulations, thermal and dynamical characteristics of supergiant 20-shell OLCF having concentric arrangement of C60@C240@ … @C24000 are explored. Fullerenes@20-shell OLCF yield larger average radii than isolated single-walled fullerenes (SWFs) at the same scale. The intershell-spacing@OLCF exhibits a reduction tendency from inner to outer shells, but is higher than that of bulk graphite. Because of nonbonded intershell forces, fullerenes@20-shell OLCF are energetically favorable over the corresponding isolated SWFs. In contrast to nonmonotonic variation of melting point with size and shell-index in SWFs and other nanoparticles, an anomalous shell-dependent melting instability in the 20-shell OLCF is identified due to the combined effects of geometrical size, nanoconfinement and surface; Both inner and outer fullerenes are not so resistive against heating, nor are they as strong as the identical-size isolated SWFs, however, the intermediate shells, locally similar to curved graphite, demonstrate higher heat-resisting property than identical-size isolated SWFs. Topological analysis reveals morphological transformation of four stages involving Stone-Wales rearrangement, heterogeneous defects nucleation, amorphization and fragmentation.

Tribochemical Competition within a MoS2/Ti Dry Lubricated Macroscale Contact in Ultrahigh Vacuum: A Time-of-Flight Secondary Ion Mass Spectrometry Investigation.

Controlling and predicting the tribological behavior of dry lubricants is a necessity to ensure low friction, long life, and low particle generation. Understanding the tribochemistry of the materials as a function of the environment is of primary interest as synergistic effects exist between the mechanics, the physicochemistry, and the thermodynamics within a contact. However, in most studies the role of the coating internal contaminants in the process is often discarded to the benefit of a more common approach in which the performances of the materials are compared as a function of different atmospheric pressure environments. The study focuses on the understanding of the tribochemical processes occurring between the materials and their internal contaminants inside an AISI440C contact lubricated by a MoS2/Ti coating. Time-of-flight secondary ion mass spectrometry is used to study at the molecular level, the material before and after friction. Friction tests with different durations are performed in ultrahigh vacuum at the macroscale to stay relevant to the real application (space). The adsorption/desorption of gaseous species during friction is monitored by mass spectrometry to ensure reliable study of the tribochemical processes inside the contact. The study shows that a competition exists between the Ti- and MoS2-based materials to create the appropriate lubricating materials via (i) recrystallization of MoS2 materials with creation of a MoS xO y material via reactions with internal contaminants (presumably H2O), (ii) reaction of Ti-based materials with internal contaminants (mostly H2O and N2). The biphasic material created is highly similar to the one created in both humid air and dry N2 environments and providing low friction and low particle generation. However, the process is incomplete. The study thus brings insight into the possibility of controlling friction via a rational inclusion of reactants in a form of contaminants to control the tribochemical processes governing the low friction and long life.

How To Measure Work of Adhesion and Surface Tension of Soft Polymeric Materials

Knowledge of the work of adhesion and surface tension directs the design of new materials for coatings, adhesives, and lubricants. We develop an approach to determine both properties from analysis of equilibrium indentations of rigid particles in contact with soft polymeric materials. In accord with coarse-grained molecular dynamics simulations, the indentation depth is described by the crossover expression combining together the adhesion and wetting models, which takes into account both the elastic energy of the contact and full surface free energy change outside and inside the contact area. The crossover expression is applied to obtain the work of adhesion and substrate surface tension for polystyrene (PS), carboxyl-modified polystyrene (PS-COOH), and poly(methyl methacrylate) (PMMA) particles in contact with poly(dimethylsiloxane) (PDMS) networks made of brush-like and linear chains. This analysis results in the work of adhesion W = 48.0 ± 2.9 mN/m for PS/PDMS, W = 268.4 ± 27.0 mN/m for PS-COOH/PDMS, a...

Identification and characterization of the degradation products of prasugrel hydrochloride tablets using LC-MS technique

ABSTRACTNew high-performance liquid chromatography method was developed for the determination of prasugrel HCl-related substances. Impurity profile of prasugrel HCl was established by studying the degradation profile of it as an active pharmaceutical ingredient, for the first time, in the tablet form. Two significant unknown degradation products (impurities) were detected and characterized, to the best of our knowledge; these impurities have not been previously reported in the literature. The first one resulted from acidic, basic, and neutral hydrolyses of prasugrel; it was nominated as impurity 1 (5-(2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridin-2(3H)-one), its structure was proposed using liquid chromatography/mass spectrometry technique. The second degradant was nominated as impurity 2 (5-(2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl)-7a-hydroxy-5,6,7,7a-tetrahydrothieno[3,2-c]pyridin-2(4H)-one) that formed upon neutral hydrolysis of prasugrel with magnesium stearate; this impurity was identified using nuclear magnetic resonance and LC-MS techniques. Based on these findings, other lubricant materials should be used in prasugrel tablets instead of magnesium stearate to avoid formation of such impurity. Prasugrel HCl was susceptible to hydrolytic and oxidative degradation, whereas it was stable under these conditions.

Auxetics and Other Systems of Anomalous Characteristics

Auxetics and Other Systems of Anomalous Characteristics

A numerical study on the contact fatigue life of a coated gear pair under EHL

PurposeCoatings are widely used in gears to keep interface from wearing excessively. The purpose of this paper is to study the effect of coating properties and working conditions on the pressure, the shear traction, stresses as well as the fatigue life of spur gear.Design/methodology/approachA numerical contact fatigue life model of a coated spur gear pair under elastohydrodynamic lubrication (EHL) is developed based on the characteristics of gear geometry and kinematics, lubrication conditions and material properties. Frequency response functions and the discrete convolute and fast Fourier transform (DC-FFT) algorithm are applied to obtain elastic deformation and stress. Mutil-axial fatigue criteria are used to evaluate the contact fatigue life based upon the predicted time-varying stress fields of coated bodies.FindingsThe maximum Mises stress decreases while the fatigue life increases as the coating modulus decreases. A thinner coating leads to a longer life and a smaller maximum Mises stress for hard coatings. The load has more significant effect on the contact fatigue life of soft coatings.Originality/valueThe developed model can be used to evaluate the contact fatigue life of coated gear under EHL and help designers analyze the effect of coating elastic modulus and thickness on the contact pressure, film thickness and stress.

Experimental investigation and model development of the non-Newtonian behavior of CuO-MWCNT-10w40 hybrid nano-lubricant for lubrication purposes

Nanofluid lubricants demonstrate superior thermal and mechanical characteristics compared with the traditional bare lubricating oils. Here we added cupper-oxide nano-particles and Multi-Wall Carbon Nano-tubes (CuO-MWCNT (9:1)) into a commericial lubricating oil (10w40) and achieved prominent rheological behaviors. The hybrid nano-particles and 10w40 were mixed with different volume fractions (0–10%). Viscosity of the issued nano-composite fluids was measured under different tempetures (5–55°C) and shear rates. It was inferred that CuO-MWCNT (9:1)-10w40 possesses non-Newtonian rheological characteristics, same as it's bare analogous. The experimental data were firstly approved by Ostwald de Waele model, and then used to develop a novel mathematical model, correlating the volume fraction of the solid phase and the operating temperature to the viscosity of the composite nano-fluid. In order to further validation, an artificial neural network (ANN), based on multilayer perception (MLP) algorithm, was created and applied to support the rheological behavior of the prepared nano-fluids. The regression coefficient (R2) and the mean squared error parameter (MSE) were respectively determined to be 0.9992 and 1.81E−4. It was concluded that the CuO-MWCNT (9:1)/10w40 nano-lubricant complies the essential requirements of a highly effective lubricant material, and suggested numerical model is a reliable tool, to describe the rheological behaviors of the nanofluid lubricants, with various contents of nano-particles, in a wide range of operating temperatures.

Experiment study on tribological performances of GNPs/MoS2 coating

Abstract Graphene is considered as a promising lubrication material due to its high stiffness, strength and good thermal conductivity. Therefore, it is feasible to add graphene nanoplatelets (GNPs) in molybdenum disulfide (MoS2) to improve the tribological performances of the latter. Past studies on graphene/MoS2 focused mainly on its numerical simulation, while associated experimental researches are seldom reported. In the present study, the GNPs/MoS2 and MoS2 coatings are fabricated on GCr15 steel (i.e., the test piece) by air spraying. Then effects of the GNPs content on the coefficient of friction (COF) and wear of the coating are investigated experimentally. The experimental results show that the addition of GNPs can effectively improve the tribological performances of MoS2 coating. The COFs and wear of GNPs/MoS2 coating are related closely to the applied load and rotational speed of the disc.