This study investigated the progression of Type IV damage in the heat-affected zones (HAZ) of welded joints in high-Cr ferritic steels, specifically ASME Grades 91 and 122, using electromagnetic acoustic resonance (EMAR), a non-contact ultrasonic measurement technique. The investigation focused on variations in ultrasonic characteristics and temperature changes induced by the thermoelastic effect. The results revealed that the initiation and growth of creep voids associated with Type IV damage led to increases in both the nonlinear ultrasonic parameters and attenuation coefficients, as well as a rise in temperature due to the thermoelastic effect. These changes are attributed to increased internal friction resulting from microstructural degradation. The findings suggest that the EMAR technique, by detecting thermoelastic effects, has significant potential for the non-destructive evaluation and early detection of Type IV creep damage in welded ferritic steel components.
ISHII et al. (Wed,) studied this question.
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