2016 Volume 102 Issue 11 Pages 630-637
The change in hydrogen thermal desorption characteristic of heat resistant ferritic stainless steel (18Cr-2.5Si steel) due to creep was investigated to examine the applicability of hydrogen as a tracer for creep damage evaluation. The hydrogen charging into the interrupted creep specimens with a wide variety of damage degrees was conducted by means of cathodic electrolysis. Next, the hydrogen-charged samples were subjected to the thermal desorption analysis (TDA) for measuring the hydrogen evolution curve. The experimental results revealed that the overall shape of curve varied with creep depending on the test conditions. However, this change in desorption characteristic reflected not only the creep damage but also the microstructural changes such as precipitation/coarsening of NbC and change in dislocation density. In an attempt to separate their effects and extract the former alone, the measured curve was decomposed into several curves by comparison with the curves of thermally aged and solution treated steels. As a result, the amount of desorbed hydrogen, which was likely to be associated with defects like a void and/or vacancy cluster, was found to increase with increasing creep damage, and it was successfully arranged with the parameter derived based on the creep void growth’s law.
