Sungjin Kwon

Evaluation of Corrosion Degradation of 12Cr Alloy Steel Using an Ultrasonic Backward Radiation

The corrosion degradation characteristics of the 12Cr alloy steel, which is widely used in fossil power plants as a turbine blade material, are evaluated nondestructively by use of the backward radiation of propagating Rayleigh wave. For this purpose, an automated system for measuring the ultrasonic backward radiation has been developed, and the frequency dependency of the Rayleigh surface wave has been investigated indirectly by observing the angular dependency of the acquired signals. The velocity of Rayleigh wave decreased as the increase of aging time, which implies the increase of the effective degraded layer thickness. And the peak amplitude of the radiation increased as aging time, which relates to the increase of inter-granular corrosion. The result observed in this study demonstrates high potential of the backward radiated ultrasound as a tool for nondestructive evaluation of the corrosion degradation characteristics of aged materials.