Cavitation Erosion Behaviour of Martensitic Stainless Steels SUS 420J2 and SUS440C by High Pressure Liquid Jet

The high-pressure cavitation erosion (CE) behavior of SUS420J2 and SUS440C were studied by a high pressure cavitating liquid jet experiment apparatus, according to ASTM Standard G134-95. The microstructures were investigated by X-ray diffraction and scanning electron microscopy to determine the phases and precipitates. The mass loss vs. exposure time relations indicated that SUS440C had longer incubation time and a decreasing erosion rate. The eroded topographical evolution was investigated, indicating that the initiation of cavitation erosion was accumulated from grain boundaries for SUS420J2, and from M3C precipitates or ferric oxide inclusions for SUS440C. The dominant factors that influenced CE behaviors changed in different cavitation stages. Micro-pitting and initial damage induced by grain boundaries or precipitates were the dominant erosion forms during the incubation stage; however, the matrix hardness started to prevail as the dominant factor after the precipitates had been torn off, or grain boundaries damage disappeared.