Influence of atmospheres on the friction and wear of cast iron against chromium plated steel at high temperatures

The aim of this study is to investigate the atmospheric effect on the wear of cast iron against chromium plated steel at temperatures up to 800 ◦C. Reciprocating wear tests of a cylinder-on-plate configuration were performed in air and a low-oxygen CO2-N2-O2 atmosphere and analyzed.
At low temperatures an adhesive wear regime with material transfer from the cast iron cylinder onto the chromium plating was observed up to 400 ◦C. Higher temperatures lead to a tribologically generated oxide layer at the interface, a so-called “glaze layer”, resulting in a strong wear decrease. The micro structural analysis reveals a layered structure of differently strong compacted wear particles consisting mainly of iron oxide Fe2O3.A modification of the surrounding atmosphere to an oxygen amount of 5 vol% showed little impact on this tribological behavior above the threshold temperature of 400 ◦C. Sufficient oxidation times of the generated wear particles were assumed, which is a necessary step of the layer formation. Based on this finding, a temperature related sintering or phase transition process is postulated to explain the glaze layer formation independently of the surrounding, oxygen containing atmosphere.
Nevertheless, for the adhesion dominated regime at temperatures below 400 ◦C, a positive influence on the wear behavior in the CO2-N2-O2 atmosphere was observed. This change in the tribological behavior is attributed to a carbon enriched layer of 400 nm thickness, which is formed by comparatively less oxidized spheroidal graphite of the cast iron.