The Influence of Applied Stress and Surface Finish on the Pitting Susceptibility of Low Alloy Turbine Disk Steels in Wet Steam

Abstract

Abstract The effects of applied tensile and compressive stresses and surface finish on the pitting susceptibility, and hence stress corrosion crack initiation, of 34CrNiMo6 and 26NiCrMoV145 steam turbine disk steels were studied. In an attempt to simulate actual conditions, all tests were conducted in an aerated wet steam environment. Four-point bend specimens were used in the study, and scanning electron microscopy (SEM) was used to examine any pits and cracks found in the specimens. It was found that 34CrNiMo6 is more susceptible to pitting than 26NiCrMoV145, that testing time influences the degree of pitting on differently machined surfaces, and that pitting susceptibility increases with increasing applied tensile stress.