CAVITATION EROSION OF BAINITIC STEEL

The cavitation erosion of a bainitic steel in distilled water has been investigated by means of a rotating-disc erosion apparatus. It was fo und that the bainitic steel specimen with higher value of impact tough ness has better cavitation resistance and the increase of the relative content of lower bainite can improve the cavitation resistance consid erably. The cavitation mechanism of bainitic steel was explored by exa mining the eroded surface and the cross-section of the specimens with optical microscope and scanning electron microscope. The cavitation da mage process of bainitic steel consists of three stages. First, the ca vitation pits and cracks are formed by the detachment of small chips i n the surface; second, the pits and cracks are enlarged and penetrated by the loss of small chips in their inside surfaces; finally, the ste pwise propagation of the pits and cracks results in the loss of massiv e chunks. It was discovered that lower bainite phase in steel can resi st the enlargement and extension of erosion pits and cracks because of its higher toughness and effective impact resistance. The surface har dening of bainitic steel during the cavitation inhibited the formation and growth of the pits and cracks, consequently the cavitation resist ance of bainitic steel increased. (C) 1998 Elsevier Science S.A.