Susceptibility of Hydrogen-Induced Stress Cracking of Duplex Stainless Steel at Elevated Temperature

Experience has shown that stainless steels can suffer from Hydrogen Induced Stress Cracking (HISC) under cathodic protection in seawater.  During the last 10 years major research projects have been executed to establish a better understanding of the mechanisms and to develop qualification methods and design procedures.  It is a common understanding that the probability of HISC initiation increase with decreased temperature.  Most of the testing has therefore been executed at room temperature or at lower temperature.  What about higher temperatures – will HISC be a problem also at temperatures above 80⁰C? 

 This paper presents results from a test program examining the HISC susceptibility of 25% Cr super duplex stainless steel (UNS S32750) at temperatures up to 150⁰C.  Both Slow Strain Rate (SSR) testing and Single Edge Notch Test (SENT) specimens were tested in 3.5% NaCl solution.  The specimens were pre-charged for 30 days and cathodically polarized to -1050 mV SCE during the exposure.  The SSR results from hydrogen charged specimens were compared to specimens tested in air (no hydrogen charging).  

 The results from the testing indicated that 25% Cr super duplex stainless steel was susceptible to HISC even at 150⁰C.