Influence of Surface Nanostructuring on the Serviceability of SShKhN Cast-Iron Rolls
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INFLUENCE OF SURFACE NANOSTRUCTURING ON THE SERVICEABILITY OF SShKhN CAST-IRON ROLLS О. V. Maksymiv,1,2 V. І. Kyryliv,1 B. P. Chaikovskyi,3 Ya. B. Kyryliv,4 L. М. Hordiichuk,3 and І. H. Yaroshovych3
UDC 622.245.002.4.
We study the wear resistance, fatigue strength, and corrosion-fatigue strength of SShKhN-42 rolls made of cast iron with surface nanostructures obtained as a result of mechanical-pulse treatment under the operational conditions of rolls of the rolling mills. It is shown that the surface nanostructure makes the wear resistance of cast iron three times higher and almost doubles the fatigue strength. This type of behavior of cast irons with surface nanostructure is scientifically substantiated. Keywords: rolls of rolling mills, SShKhN-42 cast iron, nanocrystalline structure, wear resistance, fatigue, corrosion fatigue.
Introduction Rolls of rolling mills operate under the conditions of simultaneous action of cooling aqueous media, abrasives (scale), high temperatures, impact loads, and variable contact and thermomechanical stresses [1, 2]. These operating conditions often lead to premature losses of the serviceability of rolls, which are mainly caused by their low wear resistance and the appearance of surface thermal-fatigue and contact-fatigue cracks [2]. On the other hand, in order to improve the characteristics of fatigue strength and wear resistance of heavily loaded machine parts, it is possible either to apply the procedure of surface alloying with simultaneous laser treatment [3], or to form finely divided [4] or nanocrystalline (NCS) [5] structures, in particular, by the method of mechanical-pulse treatment (MPT) [6] based on the use of the pulse energy of high-speed friction. As a specific feature of this method, we can mention the combination of dispersion of the structures, surface alloying from special working media (WM), and structural-phase transformations caused by the MPT. The improvement of the fatigue and corrosion-fatigue characteristics of the surface layers of steels after MPT was demonstrated earlier in [7] and, for the characteristics of roll steel, in [2]. In technological lines of rolling, parallel with steels, it is customary to use cast irons, in particular, for the SShKhN-42-type rolls. However, the number of available investigations devoted to the influence of the surface NCS on the physicomechanical properties of cast irons is quite small [3, 8]. Thus, the aim of the present work is to study the influence of surface nanostructures obtained by the MPT method on the fatigue strength and wear resistance of the cast iron of SShKhN-42 rolling rolls in working media. 1 2 3 4
Karpenko Physicomechanical Institute, National Academy of Sciences of Ukraine, Lviv, Ukraine. Corresponding author; e-mail: [email protected].
Hzhyts’kyi Lviv National University of Veterinary Medicine and Biotechnologies, Lviv, Ukraine. Lviv State University of Life Safety, Lviv, Ukraine.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 3, pp. 70–75, May–June, 2020. Original article su
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