Cavitation erosion behavior of Cr32Ni7Mo3N hyper duplex stainless steel

The cavitation erosion behavior of Cr32Ni7Mo3 N hyper duplex stainless steel in both distilled water and artificial seawater was investigated by a magnetostrictive-induced cavitation facility. The micrographs of damaged surfaces after cavitation for different intervals of time were observed by scanning electron microscopy(SEM). The cumulative mass loss curves and cumulative mass loss rate curves of specimens were drawn by measuring the weight loss. The polarization curves and free-corrosion potentials of specimens were measured by electrochemical workstation in the static state and in the cavitation erosion condition. A comparison of cavitation erosion resistance was performed between the material and SAF2205 steel in artificial seawater. The results show that cavitation damage firstly occurs in the ferrite weak areas and ferrite-austenite phase boundaries,then gradually expands to the ferrite phase,and the ferrite phase dissociates off at last. Its failure mode is cleavage brittle fracture. As the cavitation erosion time prolongs,the austenite phase microhardness value increases because of slip lines generating more. During the entire cavitation,the microhardness value of the austenite phase in artificial seawater is higher than that in distilled water. When the ferrite phase is largely destroyed,austenite phase damage begins to happen and drop off. Its failure mode is ductile failure. So the existence of austenite delays fracture expanding to the entire material surface. In artificial seawater,the interaction of both cavitation erosion and corrosion leads to material failure acceleration,and the cavitation erosion resistance of Cr32Ni7Mo3 N steel is better than that of SAF2205 steel.