Resistance of a high nitrogen austenitic steel to cavitation erosion

The resistance to cavitation erosion (CE) was measured using a rotating disk device for a high-nitrogen CrMn austenitic steel. The damaged morphology and microstructure characteristics in the surface layer exposed to CE were analyzed by the use of SEM and TEM. The results show that the resistance to CE of 18Mn18Cr0.5N (HNS) steel is 3.3 and 2.3 times higher than that of 0Cr13Ni6Mo (CrNi1) and 0Cr16Ni5Mo (CrNi2) steels, respectively, which are in commonly used for hydraulic turbine runners. The excellent resistance to CE of HNS steel is related to its good mechanical properties and the following microstructure changes: strengthening due to changes of dislocation configurations and the formation of substructures during CE, consumption of CE impact energy by the processes of CE-induced mechanical twins or stacking faults etc. as well as the strengthening due to the CE-induced products itself, the strengthening due to the block of strong N(C)Me covalent bond on dislocation motion and the reconfiguration of crystal lattices.