STRESS-CORROSION CRACKING OF ALLOY-600 AND ALLOY-690 IN HYDROGEN STEAM AT 380-DEGREES-C/

Reversed U bend tests have been performed on alloy 600 and alloy 690 s pecimens in a 380 degrees C hydrogen/steam environment. Cracking occur red for both materials in samples that had been subjected to a low mil l anneal temperature. The orientation of the cracks in the U bend spec imens was different for the 600 and 690 alloys due to differences in s train distributions for specimens manufactured from the different allo ys. STEM data indicates that, in both alloys, susceptibility to EAC is greatest if the grain boundaries are relatively free of carbides. (C) 1997 Elsevier Science Ltd.