2012 Volume 53 Issue 11 Pages 2028-2033
The creep of heat-resistant steel (12Cr–3.45W alloy) is experimentally characterized to estimate damages using a nonlinear ultrasonic technique. The finite amplitude method has been used to measure the ultrasonic nonlinearity parameter in all creep damaged specimens by through transmitted longitudinal wave. The microstructure showed significant changes in precipitate size and dislocation density during creep. The normalized ultrasonic nonlinearity decreases significantly in stage I and decreases monotonously in stage II and stage III. However, the ultrasonic nonlinearity increase due to the formation of creep voids in the vicinity of the creep failure region. The correlation between the microstructural changes and ultrasonic nonlinearity is discussed.