Influence of the External Polarization Potential on the Tribocorrosion Behavior of 08Kh18N10T Steel
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INFLUENCE OF THE EXTERNAL POLARIZATION POTENTIAL ON THE TRIBOCORROSION BEHAVIOR OF 08Kh18N10T STEEL V. I. Pokhmurs’kyi,1 M. S. Khoma,1 V. A. Vynar,1 Kh. B. Vasyliv,1,2 and N. B. Rats’ka1
UDC 620.194.3
We study the influence of external polarization with different potentials on the tribocorrosion behavior of 08Kh18N10T steel in contact with a corundum ball in a 3% NaCl solution. It is shown that the mechanical factor shifts the potential of pitting formation to the negative side by 0.17 V as compared with the surface without friction. The running-in time, friction coefficient, and material losses in the process of tribocorrosion qualitatively correlate with each other and depend on the applied electrode potential. It is shown that hydrogen released in the contact zone under the conditions of cathodic polarization embrittles the surface layers participating in the contact interaction. Moreover, hydrogen reduces oxide films and prevents their rapid formation on steel, which intensifies its wear. In addition, hydrogen facilitates deformation and increases the deformation zone near the friction track. Under the anodic polarization, we observe an increase in the number of pits in the friction area. Keywords: polarization, steel, tribocorrosion, deformation, pits.
Tribocorrosion is a process of degradation of materials that can be described as the transformation of contacting materials under the combined action of friction and corrosion. It is encountered in numerous engineering systems operating in conducting media. Thus, in particular, it is observed in structural elements and parts of machines in the chemical, oil-and-gas extracting and processing, and food industries, in transport, etc. [1–3]. However, the data on the tribological properties of metals and alloys in the absence of corrosion factor or on their electrochemical properties without friction are insufficient to predict the tribocorrosion behavior of a tribocouple because the friction interaction affects the corrosion characteristics of materials in aggressive media, and the corrosion factor changes the conditions of friction. This is explained, first of all, by the changes in the energy state of the surfaces of investigated friction couples affecting the rates of electrochemical reactions in various corrosion media [4, 5]. The processes of friction and wear of metals in conducting media are determined by the electrode potential, which is a fundamental characteristic of the electrochemical systems [5]. In the course of friction interaction in corrosive media, the influence of deformation on the electrode potential of the metal is especially pronounced [4–6]. The effects of the geometry of contact, the number of loading cycles, nature of the medium, properties and chemical composition of the contacting materials, their surface topographies, etc. are weaker[1–12]. The electrochemical processes in the course of friction of metals are studied in two interconnected directions: first, the application of electrochemical parameters with an aim to get the information
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