Application of ultrasonic methods for early detection of thermal damage in 2205 duplex stainless steel

Early thermal damage in 2205 duplex stainless steel which is caused by the precipitation of second phases during a short term exposure to high temperature (700 C) is investigated. Nonlinear ultrasonic measurements are performed and their results are compared with those from ultrasonic velocity and attenuation measurements. Experimental results show that the measured acoustic nonlinearity parameter is more sensitive than the ultrasonic longitudinal velocity and attenuation to the precipitation of chi and sigma phases early in the aging treatments. The results from the nonlinear ultrasonic measurements are also supported with those from the scanning electron microscopy (SEM), Rockwell C hardness and Charpy impact test. Especially notable is the close correlation between the hardness and the nonlinearity parameter. This research therefore proposes the nonlinear ultrasonic method as a nondestructive assessment means for early detection of thermal degradation of mechanical properties in 2205 duplex stainless steel. (C) 2012 Elsevier Ltd. All rights reserved.