Ion Beam Microprobe analysis for friction-induced material transfer processes in ta-C/steel and ta-C/brass pairs

A ion beam microprobe is applied for the analysis of friction-induced material transfer processes for ta-C/100Cr6 steel and ta-C/brass friction pairs. Using the appropriate combination of He and H ion beam Rutherford backscattering spectrometry and particle-induced X-ray emission spectrometry, detailed laterally- and depth-resolved information about the element composition of the friction pairs and formation of a tribo layer are obtained. The study shows the formation of a heterogeneously distributed, up to few nm thick surface layer of Fe on the surface of the ta-C coating, and the absence of a carbon transfer layer on the 100Cr6 counter body contact area after the friction treatment in high vacuum. This material combination is responsible for a high coefficient of friction of the order of 0.8. In contrast to that, a homogeneous, sub-nm thick brass transfer layer on the ta-C coating and a C- and O-rich tribolayer were formed in the central contact area of the brass counter body under ambient conditions, resulting in a low friction coefficient of 0.13.