Auger electron microscopy study of transfer film induced in an aircraft braking tribosystem

Microchemical analysis was carried out using a scanning Auger microscope on the transfer film induced in an aircraft brake tribosystem. The focus was placed on the study of the distribution of major elements in the transfer film, as well as the extent and uniformity of surface oxidation. Results showed that the as-worn surface of the transfer film consisted of large amounts of contaminant elements, primarily carbon and oxygen, along with minor quantities of S, Ca, Na, N and Cl. The transferred elements were distributed non-uniformly. The scale of the non-uniformity depended on the domain (particle) size of each component in the friction material. The high concentration and non-uniform distribution of oxygen indicated that the slide-induced oxidation process was severe and non-uniform. The carbon concentration was lower and metallic elements oxidized more severely in the high oxygen region than in the low oxygen region. With sputter time the Cu/Fe ratio continued to decrease, while the C/Cu ratio increased, suggesting that carbon was easier than copper to transfer and/or adhere to the steel suface.