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Fig.5.8. Dependence of the friction coefficient f of a steel spherical indenter with a radius of 0.3 mm on tool steel coated with an indium film on the thickness h of this coating.
The formation and destruction of secondary structures has a great influence on the coefficient of friction. So, on the dependence of the friction coefficient, according to B.I. Kostetsky, three sections can be distinguished (Fig. 9): section I, where the friction coefficient is quite high, but as the load increases for a number of reasons (in particular, due to the activation of friction surfaces, which facilitates the formation of secondary structures in the tribological contact), it decreases to some steady value (transient mode). In section II, the dependence f(N) of friction obeys the Amonton law, due to the formation of secondary structures on the friction surface, which ensure the presence of a positive gradient of mechanical properties in depth. Section II is limited by a certain critical load, at which the rate of destruction of secondary structures exceeds the rate of their formation, so that the rule of I.V., Kragelsky ceases to be fulfilled, and there is a transition to seizure, seizing and other pathological processes up to welding of the contacting surfaces, i.e. . damage mode.

Fig.5.9. Schematic representation of the dependence of the friction coefficient on the applied load: I - transient mode; II - stationary mode; III - damage mode.
As a result, in section III of the f(N) dependence, there is a sharp increase in the friction coefficient, its abrupt change, since in this case the setting of the contacting surfaces alternates, the destruction of the adhesive joints formed in this case, slippage, etc.
The generalized dependence of the coefficient of friction of metals on the speed of relative movement (in this case, sliding) of rubbing bodies, according to B.I. Kostetsky, is also characterized by three sections (Fig. 5.10): I - characterizing the normal mode of stationary friction; II - on which the pathological process is realized, which develops during the setting of the first kind (i.e., cold jamming); III - on which pathological processes of setting of the second kind develop (i.e. hot jamming).