Sliding wear performance of polymer composites under abrasive and water lubricated conditions for pump applications

Bearings made of polymer-based composites are often used when corrosive environments prevent the application of other kinds of materials [N.N., Gleitlager mit Wasserschmierung, Materialwissenschaft und Werkstofftechnik 30 (1999) S243; N.G. Fontana, Corrosion Engineering, second ed., McGraw-Hill, New York, 1978; M. Pourbaix, Lectures on Electrochemical Corrosion, Plenum Press, New York, London, 1973, ISBN 0-306-30449-X]. This is due to the chemical resistance of the polymer matrix and the possibility to tailor the friction and wear properties of such bearings by the use of various types of fillers and fibre reinforcements [R. Prehn, F. Haupert, K. Friedrich, Entwicklung von polymeren Hochleistungsgleitlagerwerkstoffen, in: H.P. Degischer (Hrsg.), Tagungsbandbeitrag 14, Symposium Verbundwerkstoffe und Werkstoffverbunde, Wiley-VCH, Weinheim, 2003, pp. S919-924]. The development of such a material for a journal bearing in pumps, transporting aggressive and abrasive fluids, is the content of this case study. Diverse material compositions were designed and investigated. One was composed of an epoxy resin matrix, highly filled, e.g. with ceramic particles (silicon carbide, i.e. SiC), to combine the ductile character of the polymer with the hardness of the ceramic. It showed an excellent wear behaviour under dry and water lubricated conditions, when operating against steel as the counterpart. Another one consisted of a polyetheretherketone (PEEK) matrix, reinforced with short carbon fibres for sealing applications. Here, an unexpected phenomenon was observed. When the experiments were carried out under water lubrication against a rotating stainless steel ring, the demineralized water strongly affected the wear behaviour of the carbon fibres. It is the purpose of the ongoing study to find out which effects, respectively wear mechanisms, take place in the contact area between both partners, and how the enhanced wear can be reduced under these severe conditions. (c) 2005 Elsevier B.V. All rights reserved.