Vapor Phase Deposition Studies of Phosphate Esters on Metal and Ceramic Surfaces

摘要

The study focuses on a novel means of lubrication for ceramics and metals at high temperatures; called vapor phase lubrication. The deposition rate and mechanisms of tributyl phosphate ester and tricresyl phosphate ester have been explored. A Thermalgravimetric Analyzer (TGA) was modified to measure the rate of surface film formation of vapor phase deposition of lubricants on metal surfaces at elevated temperatures. Results from TGA studies showed that the vapor deposition process was a complex function of substrate, time, and temperature. Tricresyl phosphate ester (TCP) and tributyl ester (TBP) were observed to produce similar amounts of film on stainless steel substrates. The observed order of metal activity was copper > stainless steel > nickel > platinum. Film formation on nickel was found to be much more rapid at 600 C than 700 C. Also, the concentration of oxygen present during deposition strongly influenced the amount of film formed. Scanning electron microscopy was conducted on TBP films formed on Si3N4, Al2O3, and alpha-SiC. The films produced contained globule and filamentous structures. The films on each ceramic were unique, demonstrating that vapor deposition is surface sensitive on ceramic substrates. High temperature friction testing was conducted on a TCP coated Al2O3 substrate. The coating reduced the friction level for alumina, thus demonstrating the potential of vapor lubrication for high temperature lubrication of ceramics.