Comparison of high temperature design codes for creep-fatigue damage evaluation

The high temperature design codes of the ASME Section III subsection NH and French RCC-MR have been compared in terms of a creep-fatigue damage evaluation for a component with weldments. Comparisons have been made for the three materials of Mod.9Cr-1Mo steel, 316L stainless steel and Alloy 800H that are included in both codes. Evaluations of a creep-fatigue damage for a welded joint were carried out according to the two design codes and the evaluation results were compared. The two codes are quite different especially in the evaluation of a creep damage, which resulted in a large difference in the creep-fatigue damage evaluation results. As a whole, it was shown that the ASME-NH was more conservative for Mod.9Cr-1Mo steel and 316:stainless steel while less conservative for Alloy 800 than the RCC-MR