Evaluating Corrosion Fatigue Behavior Through Innovative Electrochemical Analyses
Mark R. Stoudt, Richard E. Ricker
Service-life estimates based on laboratory corrosion fatigure (SN) and crack propagation (da/dN) experiments predicted that two duplex stainless steel alloys would have similar fatigue lives during service in a paper processing environment. However, one of the alloys has failed in service while the other has not. In response, a study was conducted into the microstructure, corrosion, and cracking behavior of these alloys to determine if there is a difference in properties that can explain this performance and, more importantly, why laboratory experiments failed to predict it. Scratch repassivation potential behavior of the alloys and slow strain rate (SSR) tensile tests failed to reveal any significant difference in susceptibility to cracking mechanisms such as stress corrosion cracking and hydrogen embrittlement. Potentiodynamic polarization exerpiments indicated that one alloy had a current increase below the potential where both alloys pitted. Potentiostatic exposures found that this current increase was the result of the formaiton of small microscopic pits that could propagate in only one phase of the fine duplex microstructure. When SSR tests were conducted potentiostatically in this potential range, the micro-its were found to initiate cracking. Reexamination of a service failure after careful cleaning found similar micro-pits at the origin of a corrosion fatigue crack. An electrochemical rationale for why laboratory SN and da/dN experiments failed to predict this failure mechanism is presented and discussed.
Metallurgical Transactions A-Physical Metallurgy and Materials Science
and Ricker, R.
Evaluating Corrosion Fatigue Behavior Through Innovative Electrochemical Analyses, Metallurgical Transactions A-Physical Metallurgy and Materials Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=853269
(Accessed May 28, 2023)