March 23, 2011 – NRC Decides 20 and 30 Year Old Predictions of Stress Corrosion Cracking and Crack Growth Rate Need Careful Examination

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From: Makar, Gregory
Sent: Wednesday, March 23, 2011 11:23 AM
To: Klein, Paul; Csontos, Aladar; Tregoning, Robert; Hardies, Robert
Subject: Additional crack growth rate reference

For comparison, 1981 data from M.O. Speidel (Swiss Academy of Corrosion Science) show sensitized 304 stainless steel having a crack growth rate of about 10-8 m/s (-0.030 inch/day) in 22% sodium chloride at 100°C and K=40-50 MPa M1/2 .

(The solubility of NaCI at 25C is about 36% by weight, so 22% is concentrated but not saturated.)

The graph is crack growth rate vs. temperature of DCB specimens in a constant-load test. No data for 316 SS are shown on that graph and I don’t have the original paper. I found the graph reproduced in a 1992 ASM book called, “Stress Corrosion Cracking.” So I think this just affirms our feedback that the crack growth rate depends on the details and any predicted value needs to be carefully examined.

Greg

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