The Development of Transfer Films in Ultra-High Molecular Weight Polyethylene/Stainless Steel Oscillatory Sliding

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Abstract
The friction and wear behavior of a polymer/metal oscillatory sliding system is largely dictated by the film of polymer which may form on the metallic counterface. This research utilizes scanning electron microscopy as the principal tool for examination of post-test frictional surfaces in an effort to identify the processes of film formation in an ultra-high molecular weight polyethylene pin/440C stainless steel counterface oscillatory pair. Strong adhesive junction formation at contacts leads to fibril drawing upon continued motion. Eventual fibril rupture deposits polyethylene residues upon the counterface and these residues are cumulatively smeared by the pin into a film. An increase in temperature from 15 to 30 degrees C aids the smearing process, forming a smoother film which reduces wear rate by limiting polymer/metal interaction. Comparative tests with polytetrafluoroethylene support earlier conclusions that film peeling due to weaker adhesion results in higher wear rates for PTFE than UHMWPE.