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51317--9669-Effect of Strain Rate on the Crack Growth Rate of 718 Under Cathodic Potentials

Crack growth rate (CGR) behavior of UNS N07718 was investigated as a function of K-rate in two different environments under cathodic potentials, a mild environment containing 3.5wt% NaCl and a more aggressive environment containing 0.5M H2SO4.

 

Product Number: 51317--9669-SG
ISBN: 9669 2017 CP
Author: Thodla Ramgopal
Publication Date: 2017
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Crack growth rate (CGR) behavior of 718 was investigated in two different environments under cathodic potentials i.e. 3.5wt% NaCl and 0.5M H2SO4. The crack growth rate behavior was investigated as function of displacement rate in both environments. The CGR in 3.5wt% NaCl at -1050mV SCE exhibited a plateau at various K-rates. The crack growth rate in 3.5wt% NaCl was a strong function of K-rate with higher K-rate resulting in higher crack growth rate. CGR measurements in sulfuric acid exhibit K dependence. The CGR exhibits a dependence on K-rate in sulfuric acid. CGR measured under constant displacement did give sustained CGR which was substantially lower than the values measured under rising displacement.Constant K tests were performed to understand the separate out the effect of dK/dt form the K effect. The results of the constant K tests suggest that the CGR under constant K is significantly lower than under a positive dK/dt. The above results were formulated in terms of crack tip strain rate and related to the CGR.

Key words: Crack growth rate, K-rate, Cathodic Polarization, Low cycle fatigue, Static Crack Growth

Crack growth rate (CGR) behavior of 718 was investigated in two different environments under cathodic potentials i.e. 3.5wt% NaCl and 0.5M H2SO4. The crack growth rate behavior was investigated as function of displacement rate in both environments. The CGR in 3.5wt% NaCl at -1050mV SCE exhibited a plateau at various K-rates. The crack growth rate in 3.5wt% NaCl was a strong function of K-rate with higher K-rate resulting in higher crack growth rate. CGR measurements in sulfuric acid exhibit K dependence. The CGR exhibits a dependence on K-rate in sulfuric acid. CGR measured under constant displacement did give sustained CGR which was substantially lower than the values measured under rising displacement.Constant K tests were performed to understand the separate out the effect of dK/dt form the K effect. The results of the constant K tests suggest that the CGR under constant K is significantly lower than under a positive dK/dt. The above results were formulated in terms of crack tip strain rate and related to the CGR.

Key words: Crack growth rate, K-rate, Cathodic Polarization, Low cycle fatigue, Static Crack Growth

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