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For lubrication and reduced wear of friction couples at high temperatures, such as those required by the “adiabatic” or low heat rejection engine, solid lubricants are the materials of choice. Their replenishment under operating conditions is, however, more difficult than that of liquid lubricants. Two principal approaches have been suggested: (i) reaction of the boundary surfaces with vaporized liquid lubricants [1]∗ and (ii) dissociation of a gas, stable at high temperature, at the boundary surfaces to produce a lubricating carbon [2]. Continuing work by the latter approach has demonstrated its feasibility at temperatures between 400 and 650°C with both a metallic (NiAℓ) and a ceramic surface (Si3N4 · Aℓ2O3) in a pin-on-disc tribometer for ethylene gas. Friction coefficients dropped to < 0.02.

The wear process in bearings generates a clean active surface. Carbon is known to form readily on catalytic surfaces through the reduction of carbon monoxide or hydrocarbons. Carbon, through the adsorption of hydrocarbons, water vapor, or oxygen, becomes an effective lubricant. If these three phenomena can be made to work together, a new concept of high temperature lubrication would be available for combustion engines. This paper covers initial laboratory investigations towards the development of this concept. Carbon has been successfully produced through catalytic reduction of ethylene on a variety of metallic and ceramic surfaces containing nickel. This carbon has been shown to reduce friction at a sliding interface.