The initial part of the incubation period of flow cavitation erosion on austenitic stainless steel

A microscopic investigation of the initial part of the incubation period is performed of flow-induced cavitation erosion on austenitic stainless steel. Slip lines are readily seen all over the exposed area and up to three different slip systems are observed to operate simultaneously in a single grain. The amount of work hardening (as measured by microhardness tests) due to a single collapse is found to be negligible, although a change of surface topography as well as an increase in the surface layer disorder is found. It is argued that the energy of a single indentation can be calculated from 'static' material properties and a method of calculation is presented. The energy absorbed in a single indentation is found to be comparable to the energy of a cavity which initially has a diameter of 300 mu m. It is found that the number of indentations is proportional approximately to the 3.5th power of the hydrostatic collapse pressure.