THE WATER LUBRICATED, SLIDING WEAR BEHAVIOR OF POLYMERIC MATERIALS AGAINST STEEL

The water lubricated, sliding wear behaviour of five polymeric materials has been investigated as a function of constant sliding velocities between 0.13-2.27 ms-1 and pressures of 1,3 and 5 MPa on a hardened stainless steel counterface with roughnesses which varied from 1-0.25-mu-m. The materials investigated were ultrahigh molecular weight polyethylene (UHMWPE), polyoxymethylene (POM), poly(ethylene terephthalate) (PETP), molybdenum disulphide filled polyamide 6 (PA6/MoS2) and graphite filled poly(amide-imide) (P(A-1)/GR). An increase in counterface roughness resulted in a variable increase in the wear rate for all the materials investigated. A progressive increase in sliding velocity has been shown to result in an initial increase in the wear rate followed by a decrease and finally a rapid increase for all the homopolymeric materials under virtually all the applied conditions. Only UHMWPE showed a significant drop in wear rate under low pressures at high velocity. Conversely the composite polymers exhibited a variable wear rate for all sliding velocity conditions. Generally an increase in load gave an increase in wear rate for all the materials except for UHMWPE at a counterface roughness of 1-mu-m. These findings are discussed with reference to the material constitution and properties, response to strain rate, thermal effects and counterface interactions. Explanations are advanced to account for the differences in behaviour inter alia the polymeric materials.