Influence of high temperatures on the friction and wear of highly stressed tribological systems

We investigated the atmospheric effect of exhaust components on the wear of cast iron against chromium plated steel at temperatures up to 800 °C. Reciprocating wear tests of a cylinder plate configuration were performed in air and a low-oxygen CO2-N2-O2 atmosphere and analyzed afterwards.
At temperatures above 400 °C a tribological induced oxide layer is formed at the interface, a so-called “glaze layer”, which replaces an adhesive regime and leads to a strong decrease of wear. The investigation proves a layered structure out of a porous lower and a highly compacted upper part with different chemical compositions. A change of atmospheres shows low impact on this tribological mechanism above a threshold temperature of 400 °C, assuming sufficient oxidation times of the generated wear particles, which agglomerate, were compacted and sintered due to the tribological stresses and temperatures. Based on this finding, a temperature related sinter or phase transition process is postulated to determine the glaze layer formation independently of comparable small atmospheric differences. At the adhesion dominated regime of lower temperatures a Carbon enriched layer of 400 nm thickness was observed in the CO2-N2-O2 atmosphere and is made responsible for a decrease of wear.