ELECTROCHEMICAL MONITORING OF AGING EMBRITTLEMENT OF 21 4CR-1MO STEELFOR GAS-COOLED REACTOR PRESSURE BOUNDARY-COMPONENTS/

The nondestructive testing technique is applied to evaluate the temper embrittlement of normalized and tempered 2 1/4Cr-1Mo steel; it is bas ed on the anodic polarization behavior in calcium nitrate solution. Th e steel specimen is aged at a stress of 210 MPa at 450-degrees-C for u p to 8800 h in order to examine the effect of applied stress on the en hancement of intergranular segregation of phosphorus. The secondary pe ak observed in the polarization curve for the material aged under stre ss was compared with that for the non-stressed. It can be quantified w ith the degree of intergranular segregation of phosphorus. The data su ggest that the enhancement of phosphorus segregation due to the applie d stress is only recognized after 3000 h of aging. This effect diminis hes with increasing aging time.