New sights on intergranular corrosion resistance mechanism of type 304 austenitic stainless steel by adjusting carbon contents

IGC mechanisms and/or corresponding IGC resistance mechanisms of 304 and 304L ASSs by adjusting carbon contents were systematically investigated by microstructure characterization, electrochemical and IGC tests. The results reveal that a maximum IGC degree of 304 ASS is observed at an aging temperature of 660 degrees C for 10 h based on a continuous precipitation of Cr-carbides along grain boundaries. The roles of precipitated Cr-carbides are concluded as two aspects, involving an occurrence of Cr-depleted regions and a destruction of film stability along grain boundaries. However, this IGC behavior is not linearly relevant with precipitation behavior of Cr-carbides, and a co-segregation mechanism of Cr and C atoms before a nucleation of carbides plays a decisive role in this current study. In comparison, 304L ASS (by adjusting carbon contents) exhibits a superior IGC resistance after a long-term aging treatment, which is mainly attributed to simultaneously restricting a precipitation of Cr-carbides and ensuring a continuous supply of Cr atoms toward Cr-depleted regions. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The IGC mechanisms and resistance mechanisms of 304 and 304L stainless steels were investigated by adjusting carbon contents. It was found that the maximum IGC degree of 304 stainless steel occurred at an aging temperature of 660 degrees C for 10 hours, which was due to the continuous precipitation of Cr-carbides along grain boundaries. In contrast, the 304L stainless steel with adjusted carbon content exhibited superior IGC resistance after long-term aging treatment, attributed to restrictions on the precipitation of Cr-carbides and continuous supply of Cr atoms.