Evaluation of tribological properties of synthetic lubricants under high temperature and high speed conditions

Tribological properties of synthetic lubricants of a dipentaerythritol ester (DiPE), a tripentaerythritol ester (TriPE), and a five-ring polyphenyl ether (5P4E) were evaluated using a unique oxidation stability tester and a high-temperature, high-speed ball/disc tribotester. The test conditions simulated a high-temperature (300 degrees C) high-speed (60 m/s) bearing As for oxidative stability, 5P4E showed superior oxidative stability for all parameters evaluated except for deposition. The oxidative stability of ester-based lubricants TriPE and DiPE was much superior to that of an oil specified by MIL-L-23699E (MIL), though less than that of 5P4E. DiPE and 5P4E showed a high traction coefficient even at 300 degrees C and its dependency on temperature was high. In contrast, TriPE showed a low traction coefficient under many of the test conditions and the temperature dependency was less. Overall oxidative stability and traction property results suggest TriPE may be a more suitable high-temperature and high-speed bearing lubricant than either DiPE or 5P4E.