Rolling Contact Testing of Vapor Phase Lubricants—Part III: Surface Analysis©

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Abstract
Infrared microscopy (μ-FTIR), Raman spectroscopy, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize bearing surfaces lubricated from the vapor phase. Results are presented for surface films generated with a tertiary-butyl phenyl phosphate (TBPP) and a polyphenylether (5P4E). Infrared bands consistent with inorganic poly-phosphates and phosphites were detected in deposition films generated with the TBPP lubricant. Raman shifts consistent with graphite of short range order were detected in films deposited by both lubricants. However, specimens lubricated by the 5P4E had several Raman shifts consistent with Fe2O3 and Fe3O4. Iron oxides were not detected in deposition films generated with the TBPP lubricant. AES depth profiles indicate a predominant mixture of iron and carbon in the TBPP deposition film; whereas, the 5P4E film predominately consists of iron and oxygen. Localized corrosion pitting generated with the TBPP lubricant was analyzed using AES, SEM, and EDS. The results indicate that a modified matrix rich in phosphorus, oxygen and carbon, with a corresponding depletion of iron, transcends to depths of at least 10 microns in the substrate in damaged regions. Lubrication and failure mechanisms of vapor lubricated bearings are proposed based on the results.