Indexed on: 01 Jul '04Published on: 01 Jul '04Published in: Tribology Letters
Two formulations of polyphenylether (PPE) (5P4E) were evaluated in boundary lubrication regime using a ball-on-rod type rolling contact fatigue (RCF) tester. RCF tests were conducted using VIM-VAR M50 bearing elements at a stress of 4.8 GPa. To study the lubricant's dynamic thermal stability and tribological characteristics, tests were conducted at temperatures ranging from 66 to 343 °C for a 24 h period. As expected, both formulations showed higher oxidative stability compared to the base stock by 100 °C. The dynamic thermal stability of formulation A (with tin based additive) in rolling contact tests surpassed formulation B (with an alkaline additive) by over 50 °C. At higher temperatures, the PPEs showed heavy build-up of friction polymers in the contact zone. Viscosity showed only small changes for all the three PPE evaluated. Auger electron microscopy (AES) of tested specimens showed definite presence of tin in the tribofilm. Rolling Contact Fatigue (RCF) tests were conducted at 288 °C on formulation A (PPE-A) and formulation B (PPE-B) in order to compare them to the state-of-the-art gas turbine engine lubricant MIL-PRF-7808L tested at 177 °C. The L50 fatigue life and wear of PPE-B at 288 °C are comparable to that of MIL-PRF-7808L at 177 °C.