Foil air bearing load capacity tests were conducted to investigate if a solid lubricant coating applied to the surface of the bearing's top foil can function as a break-in coating. Two foil coating materials, a conventional soft polymer film (polyimide) and a hard ceramic (alumina), were independently evaluated against as-ground and worn (run-in) journals coated with NASA PS304, a high-temperature solid lubricant composite coating. The foil coatings were evaluated at journal rotational speeds of 30000 rpm and at 25 deg C. Tests were also performed on a foil bearing with a bare (uncoated) nickel-based superalloy top foil to establish a baseline for comparison. The test results indicate that the presence of a top foil solid lubricant coating is effective at increasing the load capacity performance of the foil bearing. Compared to the uncoated baseline, the addition of the soft polymer coating on the top foil increased the bearing load coefficient by 120 percent when operating against an as-ground journal surface and 85 percent against a run-in journal surface. The alumina coating increased the load coefficient by 40 percent against the as-ground journal but did not have any affect when the bearing was operated with the run-in journal. The results suggest that the addition of solid lubricant films provide added lubrication when the air film is marginal indicating that as the load capacity is approached foil air bearings transition from hydrodynamic to mixed and boundary lubrication.

These proceedings of the 15th International Conference on Wear of Materials focus on the friction and wear of materials in various applications under different environments from the nanometer scale to the meter scale. The conference provides a unique international forum for researchers and practitioners from different disciplines to exchange latest results. Coverage includes: . Wear assessment and monitoring . Wear modeling, mechanisms, mapping and prediction . Wear-corrosion testing and control . Surface engineering for wear and wear-corrosion control . Development of new wear test methods and wear test methodologies . Wear of materials for biomedical applications . Wear of non-equilibrium materials: from atomic dimensions to the micro-scale . Wear of hard and superhard materials . Wear of materials in the earthmoving, minerals processing and mining industries