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Abstract
In this study two series of morphological fatigue tests were con-ducted with a two disk machine for TiN coated rollers as well as uncoated rollers. Surface examinations showed that 1 mu;m TiN coated surfaces underwent principally elastic deformation without coating debonding. However, uncoated surfaces were heavily deformed even after a shorter contact cycle. For the uncoated rollers, cross-sectional micrographs revealed the presence of many near-surface microcracks at an asperity scale nearly parallel to the surface. It is believed that these microcracks are initiated by asperity interaction. Metallographic examinations of the uncoated subsurface revealed a. thin layer of dark etching region corresponding to the microcrack failure region. For the coated roller, few cracks were found and the dark etching region was absent. The hard coating minimizes the surface distress and suppresses the initiation of microcracks. This explains why the fatigue life is enhanced with a thin hard coating. Cross-sectional transmission electron microscopy (XTEM) study showed a. coherent interface structure for the coated specimens. The interface after rolling and sliding contact exhibited no clear boundary compared to that of the as-deposited coating. This may indicate that a good coating adhesion can be maintained during the current concentrated contact tests.
Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference In Toronto, Ontario, Canada, October 8–10, 1990
Notes
Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference In Toronto, Ontario, Canada, October 8–10, 1990