The crack growth rate for IGSCC has been measured in two nickel base alloys, Alloy 600 and X-750, in deaerated, superheated steam between 300 and 400°C. Measurements were made using MWOL samples at stress intensities of 60 and 80 MPa√m in Alloy 600 and at 15, 30, and 60 MPa√m in X-750. The X-750 was given a two-stage aging treatment to enhance IGSCC. In both alloys the activation energy increased by a factor of two or more in going from the higher to the lower stress intensity. In the stronger X-750, the crack growth rate was over 200 times faster than in Alloy 600 at the same temperature and stress intensity.

Subject
Crack growth, Intergranular stress corrosion cracking, Stress intensity, Nucleation, Activation energy, Stress cracking, Bubbling, Tensile stress, Steam, Grain boundary, Alloys, Cracks, Voids
Keywords:
IGSCC, Alloy 600, Alloy X-750, crack growth rate, temperature
National Association of Corrosion Engineers
1991
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