Extrapolation of short-term creep rupture data - The potential risk of over-estimation

This work deals with the creep behaviour of 9-12% Cr steels in the steady-state (secondary) creep regime in order to enable a more detailed and exact description of the creep rupture strength on the basis of the Monkman-Grant relation. The stationary creep behaviour has been investigated by evaluating the creep rate and the change of stress exponent of established grades of high temperature creep resistant steels using the so-called back-stress concept. A change in creep mechanism with applied stress is clearly identified in the creep rupture curves. The impact of this change is discussed and the huge potential for over-estimation of creep strengths from extrapolated short-term creep rupture data is emphasized. (c) 2007 Elsevier Ltd. All rights reserved.