The Study Of Electrochemical Behaviors Of Turbine Rotor Steel In The Admixture Of Sulfuric Acid And Alcohol

Temper embrittlement is the third high-temperature damage type merely inferior to creep and fatigue of turbine materials. A kind of nondestructive detecting method should be developed for the insuring the running safety. The virgin materials are obtained through alloy smelts firstly. Then they are subjected to heat treatment according to the GE step cooling treatment criterion. The FATT₅₀ value of all the materials increased after the treatment, thus the virgin and the embrittled materials are obtained. The electrochemical polarization test was found to be a very good measure of embrittlement. The test results at different temperature indicate that there is an evident correlation between the characteristic current peak I3 and the FATT₅₀ value of the materials. Regard the temperature as an independent factor, multiple regression analysis is conducted considering variables which are known or are nondestructively measurable. The reason that the factors are chosen lies in the remarkable correlation between them and the FATT₅₀ value of the materials. In such way a prediction model is established. The validations of the model make clear that the effect of temperature on current is removed. As a result, a regression equation which gives an estimate of the actual FATT with the scatter of±15℃is obtained to whether the test materials or new materials. The regression model at fixed temperature has a little higher precision than the previous one.