Newly developed electrochemical evaluation method of temper embrittlement of Cr-Mo-V steel and 2.25 Cr-1 Mo steel

A nondestructive electrochemical method is developed for detection and evaluation of temper embrittlement of Cr-Mo-V Steel and 2.25 Cr-1 Mo steel. In this method, temper embrittlement can be detected and evaluated by the second peak of current density 'IP2' which appears in the anodic polarization curves measured in a calcium nitrate solution. In contrast to nonembrittled materials (couplings and de-embrittling heat-treated materials) which exhibited the dull and low second peak, the sharp and high second peak current appeared in the anodic polarization curves measured on embrittled materials. This increase in IP2 is caused by selective dissolution of embrittled (impurity-enriched) grain boundaries and that increase in IP2 has a good correlation with the shifts in FATT. Temper embrittlement can be nondestructively evaluated by IP2 measurements with high accuracy.