Comparisons of 30Cr2Ni4MoV rotor steel with different treatments on corrosion resistance in high temperature water

Three different treatments, including the heat treatment, deep cryogenic treatment and laser surface melting, were carried out on the 30Cr2Ni4MoV rotor steel. Electrochemical polarization curve and stress corrosion test at the high temperature autoclave were employed to evaluate the corrosion resistance of treated specimens in high temperature water. Results indicate that the conventional heat treatment will increase the value of K_IH for specimens with the lower yield strength, and hence reduce the susceptivity of stress corrosion cracking. However, for the deep cryogenic treated specimen, no apparent improvement was observed on the hardness and corrosion resistance due to the limited carbon precipitate and austenite transformation. In comparison, the best corrosion resistance of laser treated specimens was gained among the three-method-treated specimens according to results of the electrochemical polarization tests at temperature of 90 °C. Nevertheless, some micro-cracks produced on the tensioned surface during the fabrication of self-loaded U-bend specimen due to the large deformation, and thus lead to a decreased stress corrosion cracking resistance in the environment of high temperature water.