Effect of aqueous operating media on the low-cycle fatigue of constructional steels

Abstract

The action of aqueous corrosive media on the strength of steels under cyclic loading is determined to a significant degree by the influence of two active elements, oxygen and hydrogen, participating in the corrosion process. The authors have investigated the influence of these active elements on the strength of constructional steels under cyclic loading under conditions simulating the operating conditions of heat-transfer equipment. The metal of the samples was hydrogen impregnated with cathodic polarization. The deaerated media have an insignificant effect on the low-cycle life of 20, 15Kh2MFA, 15Kh2NMFA AND 08Kh 18N10T steels at a temperature of 120-270/sup 0/C and under the quite long influence of corrosive media at low levels of elastoplastic deformation. The action of hydrogen occluded by the plastically loaded steel with cathodic polarization led to a sharp decrease in low cycle life. The tested steels revealed different tendencies toward hydrogen cyclic fatigue. The influence of the test conditions may be determined in an analysis of the adequateness of the Lanjer-Manson model. The results of determination of the adequateness according to the Fisher criterion are shown. The norm of the logarithms of lives in the low-cycle area is practically independent of the level of deformation.