Tribochemical activity of nascent surfaces

This section considers the question, what is the role of friction-induced fresh surfaces in boundary lubrication  

As mentioned above, tribological behavior in boundary lubrication is strongly affected by surface reactions as well as by chemisorption of additives on contacting surfaces. The molecular structure of the additives is not the only parameter responsible for any particular tribochemical behavior. During the friction process, contamination layers on the outer surface are removed mechanically, leading to the fomiation of fresh, nascent surfaces characterized by 

This experimental contribution confirms previous tribological investigations, which showed that phosphate additives were effective under low load conditions (mild wear), whereas sulfides were effective under high load conditions (severe wear). The results are of particular interest in understanding the beneficial roles of some specific additives, in relation to the nature of the contacting surfaces. A major contribution of this study has therefore been identification of the additives that should be chosen for antiwear under extreme pressure conditions, as functions of wear conditions and of the particular metals and alloys in contact. It contains also some interesting observations on how gas/solid reactions can be mediated by tribological activation (i.e., via a scratch), which enhances the reactivity. 

This section addresses the questions, what kinds of tribochemicai reactions occur at the friction interface, and how do they depend on the nature of the contacting bodies and of the lubricant  

The friction of Fe/Fe contacts in UHV decreases when the superficial oxide thickness increases within a controlled range, from zero in the clean metallic state to about 4 nm. 0/Fe ratios were established by AES linescans on both 

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