Extended duration solid lubrication of rolling/sliding contacts, typical of gear teeth, comprised of self-mated steel at high temperature (540°C) by carbon deposits continuously replenished through pyrolysis of acetylene feed gases, has been confirmed using a WAM-1 test machine. Adequate lubrication, denoted by a low traction coefficient (µ<0.05), depends on a sufficient rate of solid lubricant deposition relative to the removal rate (due to wear). In the absence of lubrication, high traction coefficients (µ>0.25) and scuffing will occur. Through tests initiated under adequate lubrication conditions, the balance of rates of deposition and removal is found to be adversely affected by decreased temperature or precursor gas feed rate, or by increased normal load or sliding speed. Gradual excursions in the controlled test variables produce transitions to inadequate lubrication and scuffing as demarcated by rapid increases in traction coefficient.

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Published in the Journal WEAR
Volume 211 (1997) pages 247-253