Preparation and cavitation erosion resistance of nanocrystalline surface layer on 304 stainless steels

Cavitation erosion is a common damage form of hydraulic components. Constructing a cavitation-erosionresistant layer on the surface of hydrodynamic components can effectively prolong the service life of the equipment. In this study, 304 austenitic stainless steel was machined by a diamond blade under specific processing parameters, and a nanocrystalline layer (304-Nano) was formed by the work hardening during the machining process. The machining process also allowed strain-induced martensitic transformation, creating martensite in the nanocrystalline layer. The nanocrystalline layer had an average grain size of approximately 34.7 nm, showing a Vickers hardness of 600 +/- 30 Hv, which was much higher than that of the original 304 austenitic stainless steel (230 +/- 14 Hv). After the 15-h cavitation erosion test, the cavitation erosion rate of the 304-Nano sample was only 19.4 % that of the original ordinary 304 stainless steel, showing that the 304-Nano sample has excellent cavitation erosion resistance. Furthermore, the in-situ SEM results showed that the 304Nano sample could significantly inhibit crack propagation, which was probably attributed to its high density of grain boundaries and ultrahigh hardness. The excellent cavitation erosion resistance of the nanocrystalline layer is expected to be used as a protective material for anti-cavitation erosion applications.