304奥氏体不锈钢晶间腐蚀敏感性的非线性超声表征

利用非线性超声检测技术并辅助于XRD与微观组织分析,探讨了在650℃经过2,6,10h敏化处理的304奥氏体不锈钢样品非线性超声特征参数的变化规律。结果表明:随着敏化时间的延长,归一化非线性系数单调增大;相比于固溶试样,经2,6,10h敏化处理后样品的归一化非线性系数分别增加28%,32%,43%,意味着以非线性系数表征304不锈钢的敏化度是可行的。分析认为:晶界析出碳化物(Cr23C6)与奥氏体基体产生的错配引发了局部应变场,干扰了超声波的传播;此外,随敏化时间延长,析出相的增加进一步加剧了超声波的畸变。

Nonlinear Ultrasonic Characterization for Intergranular Corrosion Susceptibility of 304 Austenitic Stainless Steel

The variation law of nonlinear ultrasonic parameters for the samples sensitized at 650℃ for 2,6,10h was discussed using nonlinear ultrasonic testing technique and XRD pattern as well as mi-crostructure.The results indicate that normalized nonlinear parameters(β/β0 )of the samples show a monotonous growth trend with the increase of the sensitized time,and normalized nonlinear parame-ters(β/β0 )of the samples sensitized with 2,6,10h increase to 28%,32% and 43% respectively com-pared with that of the base material,meaning that it is feasible to use nonlinear parameter to charac-terize the sensitivity degree.It is analyzed that the mismatch between the carbide (Cr23 C6 )precipita-ted on the grain boundary and the austenitic matrix causes the local strain fields which interfere with the propagation of ultrasonic wave in the solid sample.In addition,the increment of precipitation phase exacerbates further the distortion of the ultrasonic with prolonging of the sensitization time.