Running-In of DLC–Third Body or Transfer Film Formation

Abstract

Amorphous carbon coatings are widely used due to their beneficial friction and wear characteristics. A detailed understanding of their behavior during running-in, apart from model tribosystems, has yet to be obtained. Multiple analytical methods were used to detect the physical and chemical changes in a ta-C coating and its thermally sprayed, metallic counterpart after a running-in procedure with pin-on-disk experiments. Both coatings exhibited changes in their surface and near-surface chemistry. The mechanisms in and on the metallic coating were identified to be a mixture of the third-body type, with the formation of gradients in the microstructure and chemistry and an additional carbon-rich tribofilm formation on top. The ta-C coating’s changes in chemistry with sp2 enrichment and lubricant element inclusions proved to be too complex to allocate them to tribofilm or third-body formation.