Based on the discussion of the factors influencing the nonlinear ultrasonic testing, the feasibility of nondestructive evaluation of HR3C fireside corrosion was investigated using nonlinear ultrasonic testing. The results show that the number of pulse string is no more than 2df/c and the installation of Hanning window is helpful to reduce the disturbance of the system, in addition, the rough surface of the sample has a significant impact on the nonlinear parameter β. The nonlinear coefficient

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... monstrates a phased growth trend as corrosion time prolongs. At the initial stage of corrosion(within 50h),there are small increments within 20% in the nonlinear coefficient, however,the nonlinear coefficient β is increased obviously with the duration time to 150h. Compared with un-corroded sample, the amplification in the sample corroded for 200h reaches to 260%. The monotonous varieties in nonlinear coefficient are consistent with the aggravation of corrosion damage,hence,it is feasible to nondestructively evaluate HR3C fireside corrosion by means of ultrasonic nonlinear testing.