Effect of temperature, normal load and pre-oxidation on the sliding wear of multi-component ferrous alloys

Abstract

During the hot rolling process the surface temperature of the rolling-mill rolls can reach values as high as 600 °C. In these conditions, oxides, which have been usually considered as friction and wear reducing agents by acting as a solid lubricant, may grow on the surface and change the tribological behaviour of the roll–strip pair. In this work, the effect of temperature, normal load and pre-oxidation on the tribological behaviour of two multi-component ferrous alloys (high-speed steel and white cast iron) is analysed. The tribological characterization was carried out by using high temperature reciprocating sliding wear tests. In the first series of tests, the temperature was varied from room temperature to 600 °C while the other tribological parameters were kept constant. In the second series of high temperature tests (600 °C) the normal load was varied from 2.9 to 75.0 N whilst the other tribological parameters were kept constant. Finally, in the third series of experiments, the alloys were pre-oxidized in air at different temperature and then tested under constant tribological parameters. The test temperature and normal load had a strong influence on the wear rate, measured by means of laser interferometry. For both materials, wear rate was higher at room temperature. High-speed steel had a much lower wear rate than high chromium cast iron. Pre-oxidation did not cause a significant influence on the tribological behaviour of either material. SEM-EDS analysis show that an increase in test temperature and normal load facilitates the generation of oxide and assists in the compaction of the debris, thus producing a wear protective layer and, as a consequence, a reduction in wear rate as well as in friction coefficient.