The Composition of Surface Layers Formed in a Lubricated Cam/Tappet Contact

[+] Author and Article Information
P. A. Willermet, J. M. Pieprzak, D. P. Dailey, R. O. Carter, N. E. Lindsay, L. P. Haack, J. E. deVries

Ford Motor Company, Research Laboratory, Dearborn, MI 48121

J. Tribol 113(1), 38-47 (Jan 01, 1991) (10 pages) doi:10.1115/1.2920601 History: Received February 15, 1990; Revised June 15, 1990; Online June 05, 2008


The frictional behavior of two oils was measured in a cam/tappet friction apparatus using a direct acting bucket tappet geometry. One oil contained a soluble molybdenum friction modifier. The tappet was equipped with a removable friction disk, which allowed the frictional surface to be easily removed for surface characterization using surface profilometry, reflection infrared and XPS spectroscopies. The films consisted of varying amounts of inorganic phosphates, sulfates and sulfides with zinc, magnesium, and possibly molybdenum as cations. MoS2 , expected because additives containing molybdenum and sulfur were present, was not detected. The detection limit was less than 0.1 atom percent Mo. The film formed by the friction modified oil was thinner, smoother and contained small amounts of molybdenum. While the smooth surface finish could reduce friction by improving microelastohydrodynamic lubrication, friction reduction could not be tied to any of the chemical structures detected in these experiments.

Copyright © 1991 by The American Society of Mechanical Engineers
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