High Temperature Lubrication of Rolling Contacts with Lubricants Delivered fromthe Vapor Phase and as Oil-Mists

摘要

Several classes of synthetic lubricants were investigated as vapor phaselubricants, using a ball-on-rod tester. In general, lubricants containing phosphorus demonstrated the best high temperature performance with sustained operation at temperatures above 600 deg C in an air environment. After testing, bearing surfaces were analyzed using FTIR, Raman spectroscopy, SEM, EDS, and AES. Condensed phosphates and graphite were identified on surfaces lubricated with a tertiary butyl phenyl phosphate (TBPP) lubricant and also with a cyclophosphazene lubricant. Abrasive iron oxides, with significantly less graphite, were identified on surfaces lubricated with a polyphenylether lubricant. The difference in deposition films is attributed to the phosphate structure formed by the organophosphorus lubricants. Additionally, AES depth profiles indicate that mass diffusion is involved in the formation of vapor deposition films for several of the lubricants tested. Subsurface stress gradients and chemical surface reactions participate in the diffusion process. Candidate lubricants were also evaluated in full scale bearings at gas turbine engine conditions. The TBPP lubricant, T15 bearing steel, silicon nitride rolling elements, C-C composite bearing cages, and oil-mist delivery provided the best performance; demonstrating sustained operation at temperatures up to 450 deg C, stress loads up to 1.8 GPa, and bearing speeds of 1.3 MDN. These conditions represent the limitations of the bearing tester, not the technology itself.