Phase transformation during cavitation erosion of a Co stainless steel

Cavitation erosion is a surface degradation mechanism that affects hydraulic turbine blades. Materials have been developed in order to minimise the detrimental effect. This work uses a Co stainless steel specially developed to exhibit improved cavitation resistance. The role of the γ austenite to ε-martensite phase transformation during cavitation erosion is assessed and the influence of surface finish on the cavitation erosion behaviour is evaluated as welded surfaces were ground and remelted before ultrasonic cavitation testing. Results reveal that structure refinement due to remelting contributes to a longer incubation period and that phase transformation is responsible for up to 25% of this erosion stage.