Zinc oxythiomolybdate (ZnMoO2S2) powder as a solid lubricant for high‐temperature rolling contact applications

Abstract

AbstractConventional liquid lubricants being used in today's gas turbine engines will not be able to operate effectively in the hostile bearing environments expected in future turbine engines. The expected high operating temperatures (500–800°C) mandate new and innovative lubrication schemes to achieve success. Recent studies have demonstrated that a new class of solid lubricants, the complex chalcogenides or metal ocythiomolybdates, have good potential for high temperature lubrication. This paper describes the friction, wear and rolling contact endurance of three high‐temperature bearing materials using a zinc oxythiomolybdate (ZnMoO2S2) powder lubricant. Rolling contact tests were conducted using VIM‐VAR M50, micromelt T15 tool steels and silicon nitride (Si3N4) at temperatures ranging from 23°C to 649°C, using a modified ball‐on‐rod type rolling‐contact fatigue tester. Significant improvements in friction, endurance and wear were observed at all test temperatures, and with all three materials evaluated, when ZnMoO2S2 was used as a lubricant. Overall, silicon nitride exhibited the best frictional and antiwear performance. The lubricant powder exhibited the best tribological performance with T15 and M50 specimens between 177°C and 316°C. Energy Dispersive X‐Ray Analysis (EDAX) of wear tracks showed the presence of iron (Fe) on the Si3N4 specimens as well as the presence of zinc (Zn) on both the T15 and the M50 specimens.