Nonlinear ultrasonic characterization of precipitation in 17-4PH stainless steel

• Nonlinear ultrasonic measurements using Rayleigh waves are performed on isothermally aged 17-4PH.
• The acoustic nonlinearity parameter decreased with increasing aging time of 17-4PH.
• Microstructural analysis showed evidence of increasing copper precipitation with increasing aging time.
• This work shows the applicability of nonlinear ultrasound to nondestructively monitor copper precipitation.

This research is part of a broader effort to develop a nondestructive evaluation technique to monitor radiation damage in reactor pressure vessel steels, the main contributor being copper-rich precipitates. In this work, 17-4PH stainless steel is thermally aged to study the effects of copper precipitates on the acoustic nonlinearity parameter. Nonlinear ultrasonic measurements using Rayleigh waves are performed on isothermally aged 17-4PH. Results showed a decrease in the acoustic nonlinearity parameter with increasing aging time, consistent with evidence of copper precipitation from hardness, thermo-electric power, transmission electron microscopy, and atom probe tomography measurements.