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Exhaust gases from internal combustion engines contain appreciable quantities of various hydrocarbons and carbon monoxide. Solid carbon formed by decomposition of these gases on tribosurfaces could replace circulating lubricating oil, especially in low heat rejection engines. Experiments with silicon nitride in a pin-on-disc tribometer operating at 520°C, 2.2GPa contact pressure and 4.4cm/s sliding speed have demonstrated that friction and wear can be reduced by over 90% of their unlubricated values when ethylene, acetylene, and carbon monoxide and hydrogen are directed into the contacts. The lubricating deposit composition and morphology have been evaluated and compared in terms of effectiveness.

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.