Impact of solution conductivity and crack size on the mechanism of environmentally assisted crack growth in steam turbines

Abstract

An overview is presented of recent experimental measurements of environmentally assisted crack growth rates for steam turbine blades in simulated condensate solutions. The most notable observation is the complex dependence of stress corrosion and corrosion fatigue crack growth rates on crack size and solution conductivity in the low conductivity solutions associated with turbine condensates. Recent modelling of crack electrochemistry for this system has enabled rationalisation of most of these observations. An intriguing implication of the merging of experimental data and modelling is that the mechanism of cracking could also be dependent on crack size and solution conductivity.