Nanostructured surfaces

Resistance of surface nanocrystalline and ultrafine-grained structures to wear and cavitation erosion damage
Y. B. Kyryliv1, V. I. Kyryliv2, B. R. Tsizh3,4, O. V. Maksymiv2
1Lviv State University of Life Safety, 35 Kleparivska St., Lviv 79007, Ukraine
E-mail: yaroslav_kyryliv@ukr.net

2Karpenko Physical-Mechanical Institute of the NAS of Ukraine, 5 Naukova St., Lviv 79060, Ukraine

3Kazimierz Wielki University in Bydgoszcz, 30 Chodkiewicza St., Bydgoszcz 85-064, Poland, 4Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies Lviv, 50 Pekarska St., Lviv 79010, Ukraine

One of the effective methods for the formation of surface nano- and ultrafine-grained structures is severe plastic deformation. Among them are mechanical pulse treatment (MPT) and vibration-centrifugal hardening (VCH). During MPT [1], the fragmentation of the structure occurs due to the use of high-speed friction energy of the treated surface and a special metal hardening tool. A nanocrystalline structure is formed with a high microhardness up to 8-12 GPa and regulated by processing modes with a depth of up to 500 microns. The VCH [2] compares favorably with the existing methods of vibration processing by the design of a special cylindrical reinforcing tool with balls fixed in it around the perimeter. Such conditions increase contact stresses in the contact zone, deform and fragment the grain structure with high microhardness (7-9 GPa) and increased depth of the hardened layer to 5-6 mm. This makes it possible to carry out additional finishing operations for finishing for high precision surfaces. Both techniques form residual compressive stresses in the surface layers. It was shown that nano- and ultrafine grain surface structures have a reduced friction coefficient, which is obviously due to a change in the electronic configuration caused by high compression stresses in the grains. The influence of treatments on the wear resistance in an oil, oil-abrasive medium and the resistance to cavitation erosion damage is investigated. Their advantages are shown in comparison with traditional methods of heat treatment.

1.	V. I. Kyryliv, “Surface saturation of steels with carbon during mechanical-pulse treatment,” Materials Science, vol. 35, no. 6, pp. 853–858, 1999.
2.	V. Kyryliv, Y. Kyryliv, N. Sas, and V. Dutka “Residual stresses formed by vibration-centrifugal hardening,” Advances in Materials Science and Engineering, vol. 2020, Article ID 5189473, 7 pages, 2020.