Change in Electrochemical Property of 12%Cr Ferritic Steel in 1M-KOH Solution Due to Creep

Abstract

Electrochemical material characterization method was applied to the creep specimens of 12%Cr ferritic steel to evaluate the changes in precipitates during creep. Experimental results revealed that the peak current densities “Ip1” and “Ip2” appeared at specific potentials during anodic polarization curve measurement in 1M-KOH solution. These peak current densities corresponded to the selective dissolution of several kinds of precipitates, respectively. The Ip2, which reflected the amount of M23C6 and Laves phase, increased more siginificantly with creep than thermal aging. On the other hand, the effect of applied stress was not reflected on the change in Ip1, although it increased with thermal aging and creep as well as the Ip2.

Advanced technology in creep life prediction and damage evaluation for creep strength enhanced ferritic steels

“…In this case, it was seen that the peak current density I p for Gr.92 increased with thermal aging and creep, and corresponded to the selective dissolution volume of M 23 C 6 and Laves phase. Figure 13 [44] shows electrochemical measurement results for Gr.122 under similar test conditions indicating two peak current densities at around À 250 mV and þ 250 mV, respectively, and increase of these peaks in terms of creep life fraction. However there is no effect of stress for the I p1 which should be the thermally dominant factor, in contrast the effect of stress is significantly observed for I p2 if the data are compared between grip portion and gauge portion.…”