OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 1 2022 Fig. 6. Correlation between erosive wear and the intensity of martensitic transformation during cavitation A strong effect of martensitic transformation on cavitation erosion resistance was also shown for austenitic steel 304 [37, 38], which is similar in alloying system to the considered AISI 316 steel and E308L-17 coating. Thus, it can be concluded that cavitation loading of the 60Cr8TiAl coating leads to a phase transformation (γ → αʹ), similar to abrasive action. This causes synergistic effects inherent in metastable austenitic steels, such as increased hardness, energy dissipation, and increased stresses in the surface layer. The result of these effects is increasing the cavitation resistance of 60Cr8TiAl coating in comparison with widespread materials used for parts operating in applications requiring cavitation resistance. Conclusions 1. The mechanism of surface hardening in metastable austenitic steel during cavitation is shown and confi rmed. In the initial period of testing, deformation martensite (α′) is formed in the surface layer. Subsequently, additional strain hardening of previously formed dispersed α’-martensite crystals occurs. 2. Cavitation effect on the surface of metastable austenitic steel leads to the deformation transformation of martensite, as in the cases of previously considered effects on similar steels at highly dynamic impact loads and abrasive wear. This indicates the same level of external specifi c loads for all these types of loading. 3. There is a correlation between the erosion resistance of austenitic steels and the intensity of the martensitic transformation developing under the action of cavitation. The resistance to cavitation of the 60Cr8TiAl coating, having the highest intensity of martensitic transformation, is higher than that of AISI 316L steel and E308L-17 coating by 4 and 10 times, respectively. References 1. Bogachev I.N. Kavitatsionnoe razrushenie i kavitatsionnostoikie splavy [Cavitation destruction and cavitationresistant alloys]. Moscow, Metallurgiya Publ., 1972. 192 p. 2. Singh R., Tiwari S.K., Mishra S.K. Cavitation erosion in hydraulic turbine components and mitigation by coatings: current status and future needs. Journal of Materials Engineering and Performance, 2012, vol. 21, pp. 1539–1551. DOI: 10.1007/s11665-011-0051-9. 3. Adamkowski A., Henke A., Lewandowski M. Resonance of torsional vibrations of centrifugal pump shafts due to cavitation erosion of pump impellers. Engineering Failure Analysis, 2016, vol. 70, pp. 56–72. DOI: 10.1016/j. engfailanal.2016.07.011.
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