Effect of heat treatments on the cavitation erosion evolution of AISI 420 stainless steels

Abstract

Cavitation erosion of AISI 420 grade stainless steels was investigated after different heat treatments. The steels were subjected to 20 h of cavitation erosion using an ultrasonic vibratory apparatus. The mass losses were measured, and the results were compared with material properties. The eroded surfaces were examined with X-ray diffraction, scanning electron microscopy and optical profilometry. The results suggest that the cavitation erosion resistance is heavily dependent on the carbon content and the performed heat treatment. While for 0.2 C grade the best results were achieved in as-quenched condition, quenching and partitioning should be used when the carbon content is higher. During cavitation present retained austenite transforms into martensite, which hardens the surface and reduces the cavitation erosion rate. Thus, elimination of retained austenite with cryogenic treatment is not beneficial. If the steel is quenched without partitioning or tempering, the resulting microstructure may become brittle, eventually leading to high erosion rate. The results indicate that even short partitioning heat treatment can effectively reduce the martensite brittleness without sacrificing hardness or cavitation erosion resistance.