| Cesium oxythiomolybdate, Cs2MoOS3, has been investigated as a pulsed laser deposited solid lubricant for Si3N4 bearings. First, the dynamics of pulsed laser ablation of Cs2MoOS 3 were studied. Based on film thicknesses grown at angles to the target normal, the ejected species were not markedly forward peaked (thickness = cos2.3&thetas;). In addition, there was no discernible variation in film stoichiometry with angle. The primary positive ions detected by time of flight mass spectrometry were OS+, S2 +, Mo+, Cs+, and Mo2 +. The drifted Maxwell-Boltzmann velocity distribution applied. The positive ions had energies between 120–820 eV, and likely contributed the excellent adhesion of the film to substrate surfaces.; Cesium oxythiomolybdate powders and a Cs2MoOS3/Si 3N4, mixture were heated in air and analyzed to study the compound's oxidative stability. Oxidation of Cs2MoOS3 was complex, producing cesium oxides, Cs2, MoO4, Cs 2So4, and molybdenum oxides at 600°C. Oxidation of the mixture produced cesium silicate glass in addition to the other compounds. Cesium oxides were not detected in the mixture at higher temperatures.; Cesium oxythiomolybdate coatings were produced by pulsed laser deposition and tested in sliding friction between 25 − 800°C. Several substrates were chosen to study lubricant/substrate interaction, including Si3N 4, SiC, Al2O3, ZrO2, and Inconel. Cs 2MoOS3 was a superb lubricant on Si3N4 from 600–750°C, and on SiC between 500–600°C, with coefficients of friction below 0.1. Wear protection was also excellent under these conditions. The formation of a silica scale on the substrate surface, followed by diffusion of melted cesium oxides, created a low shear strength cesium silicate glass with an optimum viscosity for lubrication. Cesium molybdate and MoO3 provided lubrication between 400–700°C, regardless of the presence of a silica scale. Coefficients of friction on non Si-containing substrates were below 0.2 at 600°C, and good wear protection was provided. |
