Cavitation erosion behavior of Cr–Mn–N stainless steels in comparison with 0Cr13Ni5Mo stainless steel

Abstract

The cavitation erosion (CE) behavior of two kinds of Cr–Mn–N stainless steels was investigated by means of an ultrasonic vibration processor and compared with that of 0Cr13Ni5Mo stainless steel, commonly used material for hydraulic turbines in China. The eroded surfaces after different CE duration were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Roughness ( R a) of the eroded surfaces was calculated from the measured profiles after different CE duration, and microhardness of cross-sections of the tested materials was also measured to indicate work-hardening ability. The results show that the CE resistance of austenitic single phase or austenite–ferrite duplex phase Cr–Mn–N steels is higher than that of the 0Cr13Ni5Mo martensitic stainless steel, which is mainly attributed to their high work-hardening ability. Different from 0Cr13Ni5Mo stainless steel, the cracks initiating in the eroded austenite of Cr–Mn–N stainless steels propagate nearly parallelly rather than normally to the surface, which is also beneficial to the resistance to CE. Low ferrite content is also found to be beneficial to improving the resistance to CE of duplex phase Cr–Mn–N stainless steels. It is supposed that in the case of Cr–Mn–N stainless steels the cavitation impingement energy could be absorbed and transferred into the inside of materials by the “forming and transferring” mode of the high hardness layer. Developing steel with high work-hardening ability and low ferrite volume content is possibly an important method to design steel with high CE resistance.