Robert L. Fusaro

Graphite Fluoride (CFx)n—A New Solid Lubricant

Friction and wear life studies were conducted on burnished (rubbed-on) films of a potential, new, solid lubricant, graphite fluoride (CFx)n. Results were compared to those of similar tests using graphite or MoS2. The comparisons showed that, at any one specific temperature, the wear lives of (CFx)n films exceeded those of graphite or MoS2. Also, the friction coefficient of (CFx)n was less than that of graphite and approximately equal to that of MoS2. The upper temperature limitation on the (CFx)n burnished films is about 400 C. The influence of the fluorine-to-carbon ratio in the compound was investigated and did not seem to be of importance in the range considered (1.12 to 0.7). Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Houston, Texas, October 14–16, 1969

Evaluation of Several Polymer Materials for Use as Solid Lubricants in Space

The tribological properties of ten different polymer-based materials were evaluated in a vacuum environment to determine their suitability for possible lubrication applications in a space environment, such as might be encountered on the proposed space station. A pin-on-disk tribometer was used and the polymer materials were evaluated either as solid body disks or as films applied to 440C HT stainless steel disks. A 440C HT stainless steel hemispherically tipped pin was slid against the polymer materials. For comparison, similar tests were conducted in a controlled air atmosphere of 50 percent relative humidity air. In most instance, the polymer materials lubricated much better under vacuum conditions than in air. Thus, several of the materials show promise as lubricants for vacuum applications. Friction coefficients of 0.05 or less and polymer material wear rates of up to 2 orders of magnitude less than found in air were obtained. One material showed considerable promise as a traction drive material. Rela...

Effect of Substrate Surface Finish on the Lubrication and Failure Mechanisms of Molybdenum Disulfide Films

An optical microscope was used to study the lubrication and failure mechanisms of rubbed (burnished) MoS2 films applied to three substrate surface finishes—polished, sanded, and sandblasted—as a function of sliding distance. The lubrication mechanism was the plastic flow of thin films of MoS2 between flat plateaus on the rider and on the metallic substrate. If the substrate were rough, flat plateaus were created during “run-in” and the MoS2 flowed across them. Wear life was extended by increasing surface roughness since valleys in the roughened substrate served as reservoirs for MoS2 and a deposit site for wear debris. In moist air, the failure mechanism was the transformation of metallic-colored MoS2 films to a black, powdery material that was found by X-ray diffraction to consist primarily of â-iron and MoO3 powders. In dry argon, the failure mechanism was the gradual depletion of the MoS2 film from the contact region by transverse flow. Analysis of the wear debris on the wear track at failure showed it...

Preliminary Investigation of Neural Network Techniques to Predict Tribological Properties

A complete evaluation of the tribological characteristics of a given material/mechanical system is a time-consuming operation since the friction and wear process is extremely systems-sensitive. As a result, experimental designs, i.e., Latin Square and Taguchi, have been implemented in an attempt to not only reduce the total number of experimental combinations needed to fully characterize a material/mechanical system, but also to acquire life data for a system without having to perform an actual life test. Unfortunately, these experimental designs still require a great deal of experimental testing and the output does not always produce meaningful information. In order to further reduce the amount of experimental testing required, this study employs a computer neural network model to investigate different material/mechanical systems. The work focuses on the modeling of the wear behavior, while showing the feasibility of using neural networks to predict life data. The model is capable of defining which input...

Effect of atmosphere and temperature on wear, friction, and transfer of polyimide films

Friction and wear experiments conducted on polyimide films bonded to 440 C stainless steel disks indicated that a wear transition (from high wear to low wear) accompanied the friction transition (from high friction to low friction). The transition was found to be atmospheric dependent as well as temperature dependent. Wear rate calculations indicated that, at temperatures above the transition, wear could be up to 600 times less than at temperatures below the transition. Transfer to metallic riders was also investigated and found to be considerably different at temperatures above and below the transition. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976

Lubricating characteristics of polyimide bonded graphite fluoride and polyimide thin films

A friction and wear life study was conducted on the use of a polyimide (PI) varnish as a binder for the solid lubricant, graphite fluoride (CF1.1)n. Also studied were the lubricating properties of PI thin films with no solid lubricant additives. For comparison, similar experiments on PI-bonded MoS2 and burnished films of MoS2 or (CF1.1)n were conducted. The best results were obtained with the PI-bonded (CF1.1)n films. The polyimide thin films (with no solid lubricant additives) did not lubricate well at 25 C; however, when heated to 100 C, low friction and long wear lives were obtained. Presented as an American Society of Lubrication Engineers paper ot the ASME/ASLE International Lubrication Conference held in New York City, October 9–12, 1972

Permanent Magnetic Bearing for Spacecraft Applications

A passive permanent magnetic bearing rig prototype was designed and constructed. The suspension of the rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. Preliminary testing led to successful operation of the bearing prototype to speeds of 5500 rpm using an air impeller. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated. Scheduled for Presentation at the 58th Annual Meeting in New York City April 28–May 1, 2003

Friction, wear, transfer, and wear surface morphology of ultrahigh-molecular-weight polyethylene

Tribological studies at 25°C in a 50 percent relative-humidity air atmosphere were conducted using hemispherically tipped 440C HT (high temperature) stainless steel pins sliding against ultrahigh-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress, and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer, and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatiguelike wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track. The origin of this particle was uncertain. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983

Friction and wear behavior of graphite fiber reinforced polyimide composites

The friction and wear rate characteristics of 50/50 (weight percent) graphite fiber-polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites. Two different polyimides and two different graphite fibers were evaluated. Also studied were such variables as the effect of adding 10 percent weight additions of powdered (CF1.1)n CdI2, or CdO; the effect of moisture in an air atmosphere; the effect of temperature; and the effect of different sliding speeds. In general, wear to the metallic riders was negligible and composite wear increased at a constant rate as a function of number of sliding cycles. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977

Mechanisms of lubrication and wear of a bonded solid-lubricant film

To obtain a better understanding of how bonded solid-lubricant film lubricate and wear (in general), the tribological properties of polyimide-bonded graphite fluoride films were studied (in specific). A pin-on-disk type of testing apparatus was used; but in addition to sliding a hemispherically tipped rider, a rider with a 0.95-mm-diameter flat area was slid against the film. This was done so that a lower, less variable contact stress could be achieved. Two stages (regimes) of lubrication were found to occur. In the first, the film supported the load and the lubricating mechanism consisted of the shear of a thin surface layer (of the film) between the rider and the bulk of the film. The second occurred after the bonded film had worn to the substrate, and consisted of the shear of very thin lubricant film between the rider and flat plateaus generated on the metallic substrate asperities. The film wear mechanism was found to be strongly dependent on contact stress. Presented at the 35th Annual Meeting in An...