Solid lubricant materials for high temperatures: A review

Solid lubricants that can be used above 300 C in air are discussed, including coatings and self-lubricating composite bearing materials. The lubricants considered are representative dichalcogenides, graphite, graphite fluoride, polyimides, soft oxides, oxidatively stable fluorides, and hard coating materials. A few general design considerations revelant to solid lubrication are interspersed

Preparation of Low Friction MoSex/nc-Mo Coatings Containing Spherical Mo Nanoparticles

The possibility of preparation of nanocomposite coatings consisting of a solid lubricant matrix (MoSex) and nanocrystalline metal particles (nc-Mo) was demonstrated using pulsed laser deposition from synthesized target MoSe2.The particles had spherical shapes and their sizes were about 5 - 50 nm. The content of the nc-Mo nanoparticles in the MoSex/nc-Mo coatings was varied by changing the laser irradiation regimes and the conditions of expansion of the laser plume from the target to substrate. It was established that the tribological properties of the nanocomposite coatings MoSex/nc-Mo are depended on the concentration of nanoparticles in the bulk of the coatings as well as on the structure of the coating matrix. The MoSex/nc-Mo coating with increased crystalline order of matrix obtained on a steel substrate reduced the friction coefficient to ~0.04 during steel ball sliding in air of laboratory humidity. Probable mechanisms of nanoparticle formation were proposed and a role of these particles in the wear of the nanocomposite MoSex/nc-Mo coatings was discussed

МИКРОЗОНДЫ ДЛЯ ОПРЕДЕЛЕНИЯ СИЛЫ АДГЕЗИИ И УДЕЛЬНОЙ ПОВЕРХНОСТНОЙ ЭНЕРГИИ МЕТОДОМ АТОМНО-СИЛОВОЙ МИКРОСКОПИИ

Results of usage of atomic force microscopy method operated in force spectroscopy mode for determining of the values of the adhesion forces between the probe tip (made from titanium powder particle with diameter of 67m) and Au, Ti, Al, TiN vacuum-deposited coatings, as well as bulk Al, Ti, stainless steel ones. Представлены результаты использования метода атомно-силовой микроскопии в режиме силовой спектроскопии для определения значения сил адгезии между поверхностью наконечника микрозонда, выполненного из частицы титанового порошка диаметром 67 мкм, и поверхностями вакуумных покрытий из Au, Ti, Al, TiN, а также компактных полированных поверхностей из Al, Ti, нержавеющей стали

Optical properties of ion beam textured metals

Copper, silicon, aluminum, titanium and 316 stainless steel were textured by 1000 eV xenon ions from an 8 cm diameter electron bombardment ion source. Simultaneously sputter-deposited tantalum was used to facilitate the development of the surface microstructure. Scanning electron microscopy of the ion textured surfaces revealed two types of microstructure. Copper, silicon, and aluminum developed a cone structure with an average peak-to-peak distance ranging from 1 micron for silicon to 6 microns for aluminum. Titanium and 316 stainless steel developed a serpentine ridge structure. The average peak-to-peak distance for both of these materials was 0.5 micron. Spectral reflectance was measured using an integrating sphere and a holraum reflectometer. Total reflectance for air mass 0 and 2, solar absorptance and total emittance normalized for a 425 K black body were calculated from the reflectance measurements

Structural-phase and Strained State of Vacuum-ARC Mo-N Coatings

The effect of substrate bias on the structural-phase and elastic stress-strained state during the formation of vacuum-arc deposited nanostructural coatings of the Mo–N system has been studied. An increase in the bias potential leads to (i) predominant [111] orientation of the growing molybdenum nitride crystals with a NaCl-type cubic lattice (γ-Mo2N phase) and (ii) the appearance of a second phase with a body-centered cubic crystal lattice that is characteristic of pure molybdenum. The elastically strained (stressed) state of the coating is determined not only by the conditions of deposition, but also by the mechanical properties of a substrate. In order to provide for formation of coatings in a high-elastic-strained (stressed) state, it is necessary to deposit coatings onto substrates with high elastic modulus, which prevent metal flow at the interface. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3480

Organic matrix composite protective coatings for space applications

Successful use of composites in low earth orbit (LEO) depends on their ability to survive long-term exposure to atomic oxygen (AO), ultraviolet radiation, charged particle radiation, thermal cycling, and micrometeoroid and space debris. The AO environment is especially severe for unprotected organic matrix composites surfaces in LEO. Ram facing unprotected graphite/epoxy flown on the 69-month Long Duration Exposure Facility (LDEF) mission lost up to one ply of thickness (5 mils) resulting in decreased mechanical properties. The expected AO fluence of the 30 year Space Station Alpha mission is approximately 20 times that seen on LDEF. This exposure would result in significant material loss of unprotected ram facing organic matrix composites. Several protective coatings for composites were flown on LDEF including anodized aluminum, vacuum deposited coatings, a variety of thermal control coatings, metalized Teflon, and leafing aluminum. Results from the testing and analysis of the coated and uncoated composite specimens flown on LDEF's leading and trailing edges provide the baseline for determining the effectiveness of protectively coated composites in LEO. In addition to LDEF results, results from shuttle flight experiments and ground based testing will be discussed

Research and development techniques for fabrication of lightweight solar concentrators addendum report

Fabrication of copper and nickel solar concentrator

Long Duration Exposure Facility M0003-5 recent results on polymeric films

The M0003-5 polymeric film specimens orbited on the LDEF M0003 Space Environment Effects on Spacecraft Materials were a part of a Wright Laboratories Materials Directorate larger thermal control materials experiment. They were selected from new materials which emerged from development programs during the 1978-1982 time frame. Included were materials described in the technical literature which were being considered or had been applied to satellites. Materials that had been exposed on previous satellite materials experiments were also included to provide data correlation with earlier space flight experiments. The objective was to determine the effects of the LDEF environment on the physical and optical properties of polymeric thin film thermal control materials, the interaction of the LDEF environment with silvered spacecraft surfaces, and the performance of low outgassing adhesives. Sixteen combinations of various polymeric films, metallized and unmetallized, adhesively bonded and unbonded films were orbited on LDEF in the M0003-5 experiment. The films were exposed in two separate locations on the vehicle. One set was exposed on the direct leading edge of the satellite. The other set was exposed on the direct trailing edge of the vehicle. The purpose of the experiment was to understand the changes in the properties of materials before and after exposure to the space environment and to compare the changes with predictions based on laboratory experiments. The basic approach was to measure the optical and physical properties of materials before and after long-term exposure to a low earth orbital environment comprised of UV, VUV, electrons, protons, atomic oxygen, thermal cycling, vacuum, debris and micrometeoroids. Due to the unanticipated extended orbital flight of LDEF, the polymeric film materials were exposed for a full five years and ten months to the space environment

Four space application material coatings on the Long-Duration Exposure Facility (LDEF)

Four material coatings of different thicknesses were flown on the LDEF to determine their ability to perform in the harsh space environment. The coatings, located in the ram direction of the spacecraft, were exposed for 10 months to the low-Earth orbit (LEO) environments experienced by the LDEF at an orbit of 260 nautical miles. They consisted of indium oxide (In2O3), silicon oxide (SiO(x)), clear RTV silicone, and silicone with silicate-treated zinc oxide (ZnO). These coatings were flown to assess their behavior when exposed to atomic oxygen and to confirm their good radiative properties, stability, electrical conductivity, and resistance to UV exposure. The flown samples were checked and compared with the reference unflown samples using high-magnification optical inspection, ESCA analysis, weight changes, and dimensional changes. These comparisons indicated the following. The 1000 A SiO(x) coating eroded uniformly, with minor changes in its radiative properties. The 100 A In2O3 coating eroded completely down to the Kapton backing, with resultant losses of reflectance. The RTV-615 showed erosion, with carbon (C) content losses, while the Si remained constant, with a doubling of the oxygen (O) concentration. The RTV-615 silicone with K2SiO3-treated ZnO changed from flat to glossy white in appearance. It lost C, was etched, and increased its O content. The upper layers showed no remaining Zn or K. Losses of reflectance occurred within certain wavelength bands. It was not possible to evaluate the experimental oxygen reaction rate using the calculated atomic oxygen fluence of 2.6 x 10(exp 20) atoms/cm(exp 2) for the exposure of these coatings during the flight. The bakeout of the coatings was not carried out prior to the flight. Hence, the coating weight and dimensional losses included losses by outgassing products

Tribology: The Story of Lubrication and Wear

Topics addressed include: lubrication and design of high speed rolling element bearings, high speed gears, and traction drives