The Friction and Wear of Thin, Sintered, Fluoride Films

Abstract

Results are presented for the bonding of thin, sintered, fluoride films of BaF2 and CaF2 with mono-aluminum phosphate. Friction and wear behavior of these films has been defined in terms of film compositional changes, film curing procedures, and substrate variations when subjected to varying levels of temperature and load. Mono-aluminum phosphate was found to greatly enhance the adhesion of the sintered fluoride film. There was a strong dependence of wear life at 1000 deg F on the mono-aluminum phosphate content of the film. Films containing 6 vol. percent phosphate appear to be near optimum and exhibited wear lives of 1,000,000 load cycles under sliding conditions in a dual rub-shoe device with friction coefficient levels in the order of 0.10 to 0.20. Near-optimum values were determined for cure temperature (950 deg C), and surface finish (23 μ in. rms) on rhodium-plated substrates. Graphite and gold were added to the aluminum phosphate bonded BaF2 : CaF2 films. Both additives were found to lower the friction coefficient at room temperature.