V. I. Kolesnikov

Study of friction and wear in the wheel-rail system by X-ray electron and auger-electron spectroscopy and quantum chemistry

The article presents the results of joint application of modern experimental and theoretical methods to analyze interatomic interactions on friction surfaces and in subsurface layers. The wear resistance of the wheel-rail system is shown to experience the effect of grain-boundary segregation, and the methods of suppressing its negative consequences are discussed. Adsorption on the iron surface of heteropolyphosphates of alkali metals, representing a new type of additive to lubricants, is studied.

Adsorption of heteropolyphosphates of alkaline metals on iron surface

The physical and chemical properties of heteropolyphosphates of alkaline metals are studied as promising antiwear and antiscoring additives to plastic lubricating materials. Quantum-chemical analysis of the interaction of the heteropolyphosphates with iron surfaces provides insight into the processes that evolve in these compounds during friction. The mechanism of opening of the heteropolyphosphatic cycles and their transition into linear structures is studied.

Thermodynamic and kinetic analyses of probable chemical reactions in the tribocontact zone and the effect of heavy pressure on evolution of adsorption processes

The paper presents thermodynamic and kinetic analyses of probable chemical reactions and adsorption processes depending on their energy, temperature, and pressure. It is shown that only lubricating adsorption films that appear on the rubbing surfaces due to mechanoactivated reactions can play a significant role in improving the tribological properties of a sliding contact. It is also demonstrated that heavy pressures in the zone of real contact between the asperities of rubbing surfaces enhance equilibrium adsorption of low-molecular-weight additives and of a number of high-molecular-weight additives to fluid lubricants.

Population of transition states of triboactivated chemical processes

The population of transition states of friction-induced chemical processes and similar thermo-induced reactions is analyzed. Friction is shown to be a unique natural phenomenon that involves the occurrence of highly inverse transition states of chemical interaction between contact material particles, as opposed to thermally populated transition states analogous in terms of the energy level of the reactions. It is found that in evaluating the population of transition states of mechano- and thermoactivated reactions, the specific chemical interactions do not matter and only the energies of the transition states of the thermo- and mechanoactivated processes are of importance.

Quantum-chemical investigation of the effect of grain-boundary segregation on wear resistance of steel

Quantum-chemical calculations of polyatomic clusters modeling the grain boundaries in the surface layer of steel are presented. Along with iron atoms, the clusters contain atoms of doping and impurity elements yielded to the boundary due to grain-boundary segregation. The effect of the chemical composition of segregants on the bond strength between the grains and, ultimately, on the wear resistance of steel is investigated. It is shown that the bond strength of segregated atoms with iron atoms in the surface layer of a metal is a substantial factor affecting the wear resistance.

Mechanoactivation in friction and the laws of sliding and rolling friction

The concepts of the collision theory and the activated complex theory, widely known in chemical kinetics and adapted to the description of contact between asperities on rubbing surfaces, are used to derive the expressions of Amontons’ law for sliding friction and Coulomb’s law for rolling friction. A semiquantitative relation between the sliding and rolling friction coefficients is found. Based on the expressions, the energy of interaction between the asperities and the friction coefficient in systems with selective transfer is estimated.

Synthesis and study of triboengineering characteristics of a new nanosize ceramic nickel phosphoromolybdate additive to greases

The work is devoted to investigation of the mechanism of secondary surface structures formed at the nanolevel and their study during frictional contact between solids separated by a lubricant film containing nanosize ceramic matter. The results of study of the NiO-P2O5-MoO3 system diagram are presented. The formation of nickel phosphoromolybdate is shown to occur in the system and its structure is studied using the methods of physicochemical analysis. Nickel phosphoromolybdate is introduced into the PUMA lubricant, employed in rail transport to oil rails and wheel flanges in order to retain the lubricating film and improve the tribological characteristics of the wheel-rail contact via realizing adaptability of the friction surfaces. This occurs at the nanolevel as well, where characteristic secondary structures are formed by the friction-induced effect of nanosize additives having mesogenic properties. The addition of nickel phosphoromolybdate stabilizes both the rheological and physicochemical properties of lubricating compositions of the PUMA series and minimizes their destruction. The molecular mechanism of the nickel phosphoromolybdate additive is also discussed in the work. The work was fulfilled within the framework of a systematic investigation of inorganic polymer phosphates used as multifunctional additives to railroad greases.

Investigation of the triboengineering characteristics of plastic railway greases with inorganic polymeric additives

It is proposed to use certain inorganic polymeric phosphates as antiwear and antiscoring additives in plastic greases in heavily loaded units of railway rolling stock. Introduction of sodium molybdophosphate into the plastic greases Buksol and GRO-M considerably reduces the friction coefficient of the steel-steel friction pair and keeps it stable over time. The molecular mechanism of the effect of the additives is considered.

Properties of Puma and Buksol lubricants modified by inorganic additives of binary polyphosphates

Results of investigations of tribotechnical and physicochemical properties of plastic lubricants, which are based on Puma and Buksol and used in heavy duty friction units of railway equipment, are presented. The search for new multipurpose polymeric additives of the inorganic nature was carried out based on physicochemical studies of phase diagrams of multicomponent systems. The influence of Puma and Buksol with the synthesized additives on characteristics of the process of friction is studied. Judgments about the mechanism of antifrictional and antiwear effect during work with these greases are stated. The base of this mechanism is the interaction of flexible links of anions of polyphosphate chains with a surface of metal. As a result, the layer of secondary structures is formed on the surface that protects the metal from wear.

Compatibility of chemical elements on grain boundaries in steel and its influence on wear resistance of steel

A quantum-chemical analysis of the interaction of atoms of alloying and impurity elements with grain surfaces in steel has been performed. The cluster model and the two-periodic slab model have been used. The compatibility of various elements with iron on grain boundaries in steel has been estimated. The results are in agreement with the known experimental data and correspond to Mendeleev’s law. The obtained dependences can be used for predicting strength characteristics of polycrystalline materials with various alloying additives.