**Abstract**

These demands more and more severe of the organs of friction lead to operating temperatures of more and more high which result in particular a degradation of materials. This is reflected by decreases of performance that could jeopardize the safety (fall of the coefficient of friction) and penalize the economic balance (increase the wear). Our study highlights the interactions between the thermal, tribology, and physicochemistry and has been designed to respond to the following three objectives: (1) characterize at the macrolevel the phenomena of thermal localization and identify their influence on the coefficient of friction, (2) correlate to the local scale these phenomena to the physical mechanisms of friction, and (3) to identify the consequences of the degradation of the material with the temperature, based on the coefficient of friction and the physical mechanisms of friction.

**Keywords:** tribology, friction, materials, steel, degradation
