Tribological behaviour of pipe coating in dry sliding contact with steel

Static and kinetic contact of a steel ball against a polyethylene coating was experimentally examined to study its friction and wear behaviour. The friction and wear experiments were run under ambient conditions with a pin-on-disk tribometer. Experiments were performed using various applied normal loads and testing times. Moreover, some hygrothermally aged coating samples were considered in order to analyze the aging effect. Before being subjected to experiments, these samples were immersed in both synthetic sea water and distilled water at a set temperature of 70 °C, for six months. The tribological behaviour of the studied coating was discussed in terms of friction coefficient, wear volume and wear mechanisms.Friction coefficient and wear volume have shown large sensitivity to the applied normal load and the testing time (or sliding distance). The analysis of worn surfaces for coating has shown the presence of small loss of material, microploughing, microcracking and especially transfer film. A good correlation was found between wear mechanisms and friction coefficient. For a quantitative approach of wear, an energetic approach was used to describe the friction and wear behaviour of such material. A linear relationship between the wear volumes and the dissipated energy was found. Finally, hygrothermal aging effect was not detected for short test durations but it was clearly observed for long sliding times.