The use of electrochemical and mechanical property correlations to monitor the degradation of Cr-Mo-V turbine casing steel

In this study, virgin and degraded Cr-Mo-V alloys were used to investigate the effect of thermal aging on mechanical and electrochemical behavior. The results are also used to propose the electrochemical polarization method for measuring material degradation based upon a relation between the corrosion characteristics and mechanical properties. The electrochemical corrosion characteristics were investigated by the potentiodynamic anodic polarization and the reactivation methods in an 50 wt% Ca(NO₃)₂ electrolyte. Small punch tests were applied to examine the mechanical properties by using a miniaturized specimen. The first current density measured from material aged for 1000 h at 630°C was higher than those obtained from other aged materials. In addition, the reactivated current density exhibited the greatest increase in value in material aged for 1000 h at 630°C. These results indicate that the material aged for 1000 h at 630°C exhibits the most severe material degradation and are consistent with results obtained from the small punch tests.