Results of the ASTM Round Robin on Creep-Fatigue Crack Growth Testing of a P91 Steel

Abstract This article summarizes the results of a round robin (RR) study begun in 2013 to evaluate ASTM E2760-10, Standard Method for Creep-Fatigue Crack Growth Testing (Superseded). Thirteen laboratories from around the world conducted testing and reported results. The test material was a creep-ductile, ASTM Grade P91 9Cr-1Mo steel. All testing was performed using nominally 50-mm-wide compact tension specimens at a test temperature of 625°C using trapezoidal waveforms with hold times of 0, 60, and 600 s. The 600-s hold time condition was the primary condition used for assessing interlaboratory variability among crack growth rates. Loading/unloading times were 2 s each. All laboratories tested duplicate specimens that were identical in all respects except for the force amplitude levels. Results from prior studies that included tensile, creep deformation and rupture, and low-cycle fatigue properties were available for the analysis of tests conducted as part of this RR testing. Crack growth rates at 600-s hold time reported by six laboratories fall within a 95 % confidence band (interlaboratory variability) separated by a factor of 6.16 when correlated with ΔK, 10.76 when correlated with measured vales of (Ct)avg, and 7.17 when correlated with calculated values of (Ct)avg.