Abstract
In this research, some nondestructive ultrasonic techniques were employed to inquire into the effect of microstructural changes induced by thermal aging and cold work on the ultrasonic response. As thermal embrittlement is a risk to the safety of nuclear power plants, a nondestructive detection method has to be developed for on-site monitoring. The austenitic stainless steel with δ-ferrite specimens were used to study the behavior of microstructural changes caused by age-treating and cold work and then examined by the velocity, attenuation, and nonlinear ultrasonic technique. The variations of the linear and the nonlinear ultrasonic parameters were related to the microstructural changes. Additionally, the experimental results suggest that the ultrasonic nonlinearity parameter of cast stainless steel is determined by the microstructure evolution caused by spinodal decomposition and the phase precipitation process.
Highlights
The cast stainless steel with a two-phase microstructure of austenite (γ) and δ-ferrite have extensively been applied in nuclear industry for a long time because of their great corrosion resistance, high mechanical strength, and good weld ability [1,2]
The high temperature is a major concern for the cast stainless steel pipe of power plants due to the microstructural changes in the ferrite phases
The results show that the aging and deformation would change both of the linear ultrasonic parameters and the nonlinear ultrasonic parameter
Summary
The cast stainless steel with a two-phase microstructure of austenite (γ) and δ-ferrite have extensively been applied in nuclear industry for a long time because of their great corrosion resistance, high mechanical strength, and good weld ability [1,2]. Some ultrasonic methods were used to evaluate the microstructural change of cast stainless steel. An inspection method known as nonlinear ultrasonic technique has proved to be sensitive enough for detection of material micro-damage and evaluation of change of microstructure. The nonlinear ultrasonic technique overcomes this limitation It transfers time-domain signals into frequency-domain to analyze the information of frequency which would be related to the discontinuities of material. The variation of microstructural change could be characterized by measuring A1 and A2 This is a feasibility study intended to characterize microstructural change of the cast stainless steel using the linear and nonlinear ultrasonic techniques. The relationship between ultrasonic parameters and the material property were correlated based on the ultrasonic responses to the variations of aging times
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