Failure evolution of steam-side oxide scales grown on T91 superheater tubes by acoustic emission technique

The damage of steam-side oxide scales grown on the high temperature components of boiler can seriously influence the safety of power plants. In this paper, the uniaxial tension test and the acoustic emission (AE) technique were used to investigate the damage evolution and the failure characteristics of steam-side oxide scales with varying thicknesses grown on T91 alloy tubes. The AE features associated with the metallographic investigation were adopted to detect the onset of each failure type of oxide scales. The frequency components of AE signals were extracted by the wavelet based method, and the quantitative correlation between failure types and AE signals was established. The surface and interface fracture toughness of the oxide were assessed by the critical state of the failure process. The results showed the quantitative damage evolution of steam-side oxide scales, and found the oxide thickness had more significant effect on critical strain than the fracture toughness of oxide scales.