Caviation erosion of bainitic steel

Abstract

The cavitation erosion of a bainitic steel in distilled water has been investigated by means of a rotating-disc erosion apparatus. It was found that the bainitic steel specimen with higher value of impact toughness has better cavitation resistance and the increase of the relative content of lower bainite can improve the cavitation resistance considerably. The cavitation mechanism of bainitic steel was explored by examining the eroded surface and the cross-section of the specimens with uptical microscope and scanning electron microscope. The cavitation damage process of bainitic steel consists of three stages. First, the cavitation pits and cracks are formed by the detachment of small chips in the surface; second, the pits and cracks are enlarged and penetrated by the loss of small chips in their inside surfaces; finally, the stepwise propagation of the pits and cracks results in the loss of massive chunks. It was discovered that lower bainite phase in steel can resist the enlargement and extension of erosion pits and cracks because of its higher toughness and effective impact resistance. The surface hardening of bainitic steel during the cavitation inhibited the formation and growth of the pits and cracks, consequently the cavitation resistance of bainitic steel increased.