Basic investigation for life assessment technology of modified 9Cr-1Mo steel

In order to develop life assessment techniques for aged components made of modified 9Cr-1Mo steel, specimens were artificially deteriorated by aging, creep and fatigue tests at elevated temperatures, and associated changes in the microstructure and mechanical properties were examined. It was observe d that aging resulted in formation of Laves phase causing a decrease in tou ghness. The creep damage in base metal could be correlated with decrease in hardness, while creep damage in weldments could be correlated with the are a fraction and density of creep voids. Creep rupture in weldments occurred in the fine-grained heat affected zone by the formation and growth of creep voids. The fatigue damage in base metal correlated to the maximum length o f a crack among micro-cracks initiated during fatigue cycles. (C) 1999 Else vier Science S.A. All rights reserved.