Langzeitiges Kriechrißverhalten kennzeichnender Kraftwerksstähle

Abstract

Long Term Creep Crack Behaviour of Typical Power Plant SteelsThe creep crack behaviour of the steels was investigated in a wide loading range up to a test duration of 40 000 h and down to a creep crack growth rate of 2 .r n d h with specimens of different shape and size. For steels of type l%Cr-l%Mo-0.6%Ni-0.3%V, 1% Cr-0.9%Mo-0.7% Ni-03. %V, 12% Cr-1% Mo-0.3% V-0.22% C and 12%Cr-l%Mo-O.3%V-O,2O%C tested at 550°C, the creep crack growth rate could be described by the parameter C2* with significantly smaller scatter bands than by the parameter C1* or the stress intensity factor KI. For steel 12%Cr-2%Ni-l%Mo tested at 450 "C, parameter KI leads to the smallest scatter band. The creep crack initiation can be described in a two-criteria diagram based on nominal stress and stress intensity factor. However the method is assumed to be over-conservative in case of increasing specimen size. As a result of several aperiodic creep fatigue crack tests, precracking under fatigue conditions gave a weak increase of the creep crack growth rate whereas by precracking under creep conditions the fatigue crack rate was strongly decreased.