Elevated pitting wear of injection molded polyetheretherketone (PEEK) rolls

The increased pitting wear of PEEK rolls applied as bearing elements in drawer guide rails was investigated. Similar to findings for PEEK gear wheels the increased pitting occurred only in the presence of lubricants. Simple assumptions found in literature to explain this effect for PEEK gear wheels could be disproved within this research. Moreover, high irreversible deformations during the rolling process of PEEK rolls which were observed in a previous study were shown to not influence the mechanical properties of the surface material significantly. Additionally, the chemical analysis of the tribological system with Raman spectroscopy excluded a chemical reason for the intensified pitting. A detailed microscopic analysis of unstressed PEEK rolls combined with microtome cuts of the surfaces showed distinct pre-cracks in the outermost surface region which were not visible to the naked eye. Assuming a crack growth mechanism that was strongly supported by the fluid pressure of grease enclosed in the surface pre-cracks the injection molding process was adapted in order to improve the surface quality of the PEEK rolls. By this way the fatigue lifetime of the latter was increased by a factor of 2-3 which was crucial for the practical application. (C) 2012 Elsevier B.V. All rights reserved.