Creep failure prediction from observation of microstructure in 2 1/4%Cr-1%Mo steel

An attempt has been made to demonstrate that the lifetime of 2 1/4%Cr-1%Mo steel, stressed at elevated temperatures, can be predicted by making measurements on the microstructure under accelerated creep conditions. An understanding of the creep processes involved is not considered necessary. The technique depends on the assumption, verified by experimental observation, that the different processes operating during creep, from precipitation growth and recovery to void formation, are all equally dependent upon temperature changes given by an Arrhenius equation modified by McLauchlin. It is possible to accelerate the microstructural changes in a 2 1/4%Cr-1%Mo steel, a typical power plant material, by a factor of 100 through increasing the temperature by 1000C and keeping the stress constant. The remaining lifetime of power plant components could be estimated, either by taking samples of the components themselves or, alternatively, if the operational temperatures could be monitored and applied to creep tests running in parallel, by examining the test specimens. (author)