Bonded Molybdenum Disulfide Research Articles

Investigating the effect of LaF3 on the tribological performances of an environment friendly hydrophilic polyamide imide resin bonded solid lubricating coating

The aims of this study are to prepare a new environment friendly hydrophilic polyamide imide (PAI) resin bonded molybdenum disulfide (MoS2) solid lubricating coating and investigate the tribological properties and wear mechanism. It is concluded that the preparation of hydrophilic coating has greatly reduced usage rates of fossil fuel, in the meantime, the basic physical and chemical properties, mechanical and tribological behaviors of hydrophilic coatings with 3 wt.% LaF3 are comparable to that of solvent-based resin coatings, the generation of FeF2 and FeS significantly improves the adherence between friction pairs, and the degree of oxidation of MoS2 lubricant is effectively restrained on account of the attachment of nano-LaF3 to the surface of MoS2.

On a novel solid lubricant technique: A study on the tribological characteristics under dry slide condition

The purpose of this study is to investigate the friction and wear behavior of novel electrostatic micro-solid lubricant (EMSL) bonded molybdenum disulfide (MoS2) coatings on cemented carbide tools under dry slide condition. Pin-on-disc tribological tests between titanium alloy Ti–6Al–4 V and uncoated/coated cemented tungsten carbide–cobalt alloy (WC–Co) were carried out over a range of experimental domain of sliding speeds and normal loads. Specimen wear rate and friction coefficient were investigated. Tribological tests demonstrate that EMSL bonded MoS2 coatings provide excellent anti-friction and reasonable wear performances. The mechanism of enhanced friction and wear behavior with the MoS2 coatings is discussed. This study explores the feasibility of using EMSL coatings onto tribological components and opens a new way to implement bonded MoS2 solid lubricant coatings as a new candidate for tribological operations.

Rotational Fretting Wear Characteristics of Bonded Molybdenum Disulfide Solid Lubrication Coating

Molybdenum disulfide solid lubrication coating is prepared on the surface of LZ50 steel by bonding technology.Rotational fretting wear tests of the coating and its substrate are carried out under different angular displacement amplitudes.Dynamic analyses combination with microscopic examinations through optical microscopy,scanning electric microscope and surface profilometer are performed.The result indicate that rotational fretting regimes of coating and its substrate are only partial slip regime(PSR) and slip regime(SR).No mixed fretting regime could be observed for them.Fretting regimes of coating are changed,the range of the PSR is diminished,and the SR shift to the direction of smaller angular displacement amplitude.Compared with the substrate,friction coefficient is always lower than that of the substrate during the whole fretting cycles due to lubricating effect coming from the coating.The damage in the PSR is very slight,but in the SR,the damage mechanism of the coating is mainly delamination and tribo-oxidation.In summary,the bonded MoS2 solid lubricant coating has a significant protective effect,and presents a better capability for alleviating rotational fretting wear.

Rotational Fretting Wear Characteristics of Bonded Molybdenum Disulfide Solid Lubrication Coating

Rotational Fretting Wear Characteristics of Bonded Molybdenum Disulfide Solid Lubrication Coating

The tribological performance of selected solid lubricant films in sand-dust environments

Solid lubricant films have received considerable research attention in the last decades owing to their remarkable improved tribological characteristics. In this paper, the abrasive wear behaviour of five types of solid lubricant films (magnetron-sputtered diamond-like carbon, magnetron-sputtered molybdenum disulfide, bonded molybdenum disulfide, bonded polytetrafluoroethylene and bonded graphite) in sand-dust environment has been investigated using a reciprocating pin-on-disc test rig. The effects of applied load, amount of sand and particle size on the tribological performance of these films were systemically studied. Experimental results show that magnetron-sputtered films give excellent anti-friction and wear-resistance performances under sand-dust environments compared to bonded solid lubricant films. The significant differences of surface roughness, hardness, microstructure and intrinsic lubricating property directly lead to the different tribological performances and worn morphology. The formed composite transfer layer plays a vital role in reducing friction and wear due to its anti-friction and shielding action of the film surface from the hard metal asperities. Two main abrasive wear mechanisms (three-body rolling wear and two-body grooving wear) occur simultaneously in the tribological process under sand-dust environments. A transfer layer-hardening composite wear modeling was established to further explain the anti-wear mechanisms and friction-reducing capacity of these solid lubricant films under sand-dust environments.

An investigation of friction and wear performances of bonded molybdenum disulfide solid film lubricants in fretting conditions

The friction and wear performances of bonded MoS 2 solid film lubricants with the counterpart steel ball rubbing were investigated in fretting wear conditions in order to inquire into the load-carrying capacity and wear mechanisms of bonded MoS 2 solid film lubricants under dry friction conditions. Experimental results show that the bonded MoS 2 solid film lubricants have excellent anti-friction and wear-resistance performances within a wide load range between 20 N and 800 N and within a wide oscillatory frequency range between 5 Hz and 30 Hz. It is found through analyses of the transfer films formed in the surface of the counterpart steel ball investigated by SEM, XPS and AES, that the thickness of the transfer film formed is about 38 nm and the oxidation of MoS 2 in the transfer films does not occur during dry friction process. The high load and frequency promote the formation of a compact transfer films. The compact transfer films are believed to be the predominant mechanism giving rise to high load-carrying capacity, and excellent wear-resistance performances of the bonded MoS 2 solid film lubricants.

Influence of nanometer lanthanum fluoride on friction and wear behaviors of bonded molybdenum disulfide solid lubricating films

Influence of nanometer lanthanum fluoride (nano-LaF 3) on the friction and wear behavior of bonded molybdenum disulfide (MoS 2) solid lubricating film was investigated using an oscillating friction-wear tester under dry friction condition. The worn surface of the lubricating film and the transfer film formed on the surface of the counterpart ball were observed by SEM. The microstructure of the lubricating film filled with nano-LaF 3 and the distribution of F and La in the lubricating film were investigated with transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer, respectively. It was found that nano-LaF 3 as a filler contributes to improve the wear-resistance property of the lubricating film. The lubricating film modified with nano-LaF 3 filler exhibits better wear-resistance property than that of the lubricating film without nano-LaF 3 filler at a relatively lower load (less than 250 N) and within a wide oscillatory frequency range between 5 and 35 Hz. However, the incorporation of nano-LaF 3 filler results in small increase of friction coefficient of the lubricating film. Transmission electron microscopy (TEM) and elementally X-ray map results of the lubricating film modified with nano-LaF 3 filler indicate that partial LaF 3 nanoparticles distribute around the MoS 2 particles, while other LaF 3 nanoparticles disperse in the binder. The SEM morphology of the frictional surface shows that the filler of nano-LaF 3 is able to enhance the compactness of the frictional surface, and results in an improvement of the wear-resistance property of the MoS 2 lubricating film.

低軌道宇宙環境への曝露によるＭｏＳ２焼成膜のトライボロジー特性変化

Effects of a low earth orbit (LEO) space environment on tribological characteristics of a solid lubricant film were evaluated. The tested lubricant, which has been used for space applications, was a bonded molybdenum disulfide (MoS2) film with organic binder. Three sets of the specimen were exposed to a real LEO space environment for about 1, 2 and 3 years aboard the Service Module of the International Space Station (ISS) by the Space Environment Exposure Device (SEED) experiment. In this paper, results of friction tests in vacuum and surface analyses for the specimens exposed for 1 and 2 years are reported. The results are also compared to those of the specimens irradiated individually with atomic oxygen (AO), ultraviolet rays (UV) and electron beam (EB) on the ground.

The Damage Mechanisms under Different Fretting Modes of Bonded Molybdenum Disulfide Coating

Fretting wear tests of bonded MoS2 coating under radial and composite fretting mode have been carried out on a new fretting rig. The maximum applied load was respectively 200N, 400N and 800N with a constant loading speed of 12mm/min. Dynamic analyses in combination with microscopic examinations through SEM and XPS have been performed. Experimental results showed that such MoS2 coating exhibited an excellent radial fretting damage resistance, and its damage strongly depended upon the applied maximum loads and inclined angle under composite fretting condition. The fretting damage mechanism of MoS2 coating also discussed under different fretting modes. The XPS analysis revealed that the oxidation of MoS2 crystal was played an important role in damage. The fretting wear of MoS2 coating was mainly represented by the mechanism of delamination and oxidation wear under composite fretting conditions.

An investigation on fretting wear life of bonded MoS 2 solid lubricant coatings in complex conditions

Compared to MoS 2 coatings obtained by magnetron sputtering or ion beam assisted deposition, the MoS 2 bonded solid lubricant coatings has been widely applied in sliding wear due to a cheap technical process and good thickness. However, such coatings technology has been rarely investigated in complex fretting condition. In this work, fretting wear tests of the six novolac epoxy resin bonded molybdenum disulfide solid lubricant coatings have been carried out in various normal loads and amplitudes. The effects of various process preparations, substrate materials, and environmental conditions on the fretting wear life were investigated. Main results show that enhancing substrate hardness, increasing coating thickness, sandblasting substrate surface, and heat curing coating will improve fretting wear life to some extent while it decreases with increasing relative humidity. Oxidation effect is one of the important factors for coating degradation at high temperature.

Durability evaluation of selected solid lubricating films

An investigation was conducted to examine the coefficients of friction, wear rates, and durability of bonded molybdenum disulfide (MoS 2), magnetron-sputtered MoS 2 (MS MoS 2), ion-plated silver, ion-plated lead, magnetron-sputtered diamond-like carbon (MS DLC), and plasma-assisted chemical-vapor-deposited DLC (PACVD DLC) films in sliding contact with 6 mm-diameter AISI 440C stainless steel balls. Unidirectional ball-on-disk sliding friction experiments were conducted with a load of 5.9 N and a sliding velocity of 0.2 m/s at room temperature in three environments: ultrahigh vacuum (vacuum pressure, 7×10 −7 Pa), humid air (relative humidity, ∼20%), and dry nitrogen (relative humidity, <1%). The main criteria for judging the performance of the solid lubricating films were coefficient of friction and wear rate, which had to be <0.3 and on the order of 10 −6 mm 3/N m or less, respectively. The bonded MoS 2 and MS MoS 2 films met the criteria in all three environments. The ion-plated lead and silver films met the criteria only in ultrahigh vacuum but failed in humid air and in dry nitrogen. The MS DLC and PACVD DLC films met the requirements in humid air and dry nitrogen but failed in ultrahigh vacuum.

Effect of discontinuous hard under-coating on the life of solid film lubricant under extreme contact pressure

Wear life of bonded molybdenum disulfide film lubricant applied on discrete sections of chromium electroplated to an aluminum alloy substrate under extreme contact pressure was investigated. Block-on-ring tests with ridge-shaped, hardened stainless steel blocks and lubricant coated rings were carried out in a nitrogen atmosphere for several kinds of ring materials including this under-coating. All tests except those for the discontinuous chromium under-coating indicated large or unstable friction soon after the tests started. Discontinuous chromium coating demonstrated a stable friction coefficient of around 0.05 for a long time and the lubricant film remained intact after the test. This is because discontinuous chromium coating on aluminum substrate deformed along the shape of the ridged-block and contact pressure was decreased to several hundred MPa.

Research on high-temperature bearings : R. D. Brown, R. A. Burton and P. M. Ku, (Wright-Patterson AFB, Ohio, Flight Dynamics Lab.), (1962) 80 pp.; 15 refs. Sci. and tech. aerospace repts., 1 (1) (1963) 46. N 63–10194, Southwest Research Inst., San Antonio, Tex.

Evaluation work performed on oscillating bearings of both plain journal and self-aligning types is described. Bearing substrate materials include cermets LT-1B and LT-2 and alloys F-48 and Rene 41. Lubricants receiving extensive evaluation are a clad silver--palladium alloy, molybdenum disulfide used in cavities, and bonded molybdenum disulfide. Results include those from friction and wear evaluations, radial load capacity tests on plain journal boarings, and axial and radial load capacity tests on selfaligning bearings. The bearing specimens have a nominal diameter of 1/2 inch. Friction and wear tests are at an oscillating frequency of 31 cpm, at --90 to 1750 c- F, and at 10/sup -6/ to 10/sup -5/ mm Hg. The boaring load is 4,400to 12,000 psi. (auth)