The Effect of Temperature and Cyclic Frequency Upon Fatigue Crack Growth Behavior of Several Steels in an Elevated Temperature Aqueous Environment

Abstract

The fatigue crack propagation (FCP) behavior of several ASTM A302-B and A508-2 steels was characterized in deaerated elevated temperature aqueous environment. FCP behavior was determined over the range 121°C to 343°C at a constant value of ΔK, stress ratio, and load rise time. A complex response of FCP rates as a function of temperature was observed, and this is discussed in the light of similar results developed by others within the nuclear industry. Corrosion potentials (referenced to the standard hydrogen electrode) were measured for each of the steels over the above temperature range and comparisons are made to the observed FCP behavior. Cyclic frequency effects were studied at two temperatures, 149°C and 243°C, and these are analyzed within the “time domain” format first suggested by Shoji et al. The results, when expressed in the time domain format, clearly show regions where environmentally assisted cracking (EAC) occurs, and regions where EAC does not occur. A “threshold” for EAC was noted at 149°C, and the possibility of an EAC threshold was observed at 243°C.