Remaining-life estimation of boiler pressure parts

Abstract

One of the objectives of EPRI contact 2253-1, Estimating the Remanent Life of Boiler Pressure Parts'', was the development of a metallographic approach relating microstructural degradation of parent material to remaining life. This Report describes the work undertaken in completion of this objective. A cast of 1Cr1/2Mo steel has been creep tested in argon at stresses in the range 34--80 MPa and temperatures between 590--630{degree}C in various heat treatment states, including normalized and tempered, and overaged. Various metallurgical techniques have been used and parameters measured on the ex-creep tested specimens, for assessment of their use in remanent life evaluations. These include hardness, bulk extraction of carbides and x-ray examination of the phases present, determination of matrix solute content, x-ray determination of the matrix lattice parameter and carbide extraction replication of the structure and measurement of various interparticle spacing parameters. In application to plant the interparticle spacing can be determined from a small sample removed from the component. Either cast-to-cast bounds on the constants required by the model can be used or determinations of the cast specific constants made on the sample. Of the other metallurgical parameters examined it is concluded that the current technique of bulk extraction does not allowmore » useful determination of matrix composition nor carbide phases present. 60 refs., 80 figs., 18 tabs.« less