Studies of Low-Temperature Sensitization after Sub-Surface Damage Evolution in Austenitic Stainless Steel

Abstract

The specimens of austenitic stainless steels were machined to different strain rates (105 s −1 , 1050 s −1 , 1500 s −1 , 2100 s −1 ). These specimens were subjected to low-temperature sensitization (LTS) heat treatment. The LTS treatment was carried out at 475℃ and 575℃ for 24 h. Further, oxalic acid, double-loop electrochemical potentiokinetic reactivation (DL-EPR) were carried out. As-machined specimens were subjected to surface roughness measurements, optical microscopy, electron backscattered diffraction (EBSD), and Fourier transform infrared spectroscopy (FTIR) imaging measurements. Machined specimen exhibited more difficulty in passivation than the as-received specimen. The complete surface statistics were extracted.The specimens machined at a strain rate of 2100 s −1 were exhibited a higher degree of sensitization (DoS) at LTS of 575℃ and 475℃ for 24 h, respectively, than other specimens. It was found that specimens machined at a higher strain rate produced smoother roughness. FTIR imaging was used to extract the signal intensity of chromium oxide (Cr 2 O3) peak. Detected Cr 2 O3 peak/signal was strong for the specimen that exhibited lower DoS as estimated from FTIR-imaging.