Analysis of the tribological interaction of a polytetrafluoroethylene-lined radial lip oil seal, shaft and lubricant sample

Abstract

To investigate the tribological interaction and wear mechanisms of polytetrafluoroethylene-lined radial lip oil seals in service, a sleeve, seal and lubricant sample taken off a rotating rig are studied. The test was terminated at 72 h, after severe leakage in the final 15 h of the test. All three components are studied using a coherence scanning interferometer and environmental scanning electron microscopy to investigate wear after testing. Results show a wear band on the aerospace grade case-hardened sleeve, appearing as a ‘polished in’ area by the seal. A study of the filler content of the polytetrafluoroethylene coating uncover glass fibres, calcium carbonate, carbon and graphite layers present, assumed responsible for the wear to the sleeve. The polytetrafluoroethylene coating is a 300 μm coating, distinct from the bulk elastomer. This finding is confirmed after observing this layer on both, the tested and new seal lip. Wear of the seal lip is measured and facilitated by comparison to the identical new seal. Lastly, debris from the seal and sleeve wear are found in the lubricant sample.