Self-Lubricating Composites of Porous Nickel and Nickel-Chromium Alloy Impregnated with Barium Fluoride-Calcium Fluoride Eutectic

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Abstract
Porous nickel and nickel chromium were filled with BaF2-CaF2 eutectic composition by vacuum impregnation at 2000 F. The friction and wear properties of the resulting composites were determined in air and in hydrogen from 80 to 1500 F. Higher friction coefficients were obtained compared with coatings of the same fluoride composition on dense metals, however low wear and excellent wear life were obtained. The advantages of coatings (lower friction) and of composites (longer wear life) were combined by applying a thin sintered film (0.001-inch) of eutectic fluoride to the load-bearing surfaces of the composites. In a hydrogen atmosphere at a sliding velocity of 2000 ft per minute, typical friction coefficients for coated alloy composites were 0.06 at 1500 F, 0.18 at 500 F, and 0.20 at 80 F. Friction coefficients were higher at low sliding velocities. Composites with a nickel-chromium matrix were superior to nickel composites in load-carrying ability.

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