Fig.1 Effects of cold-rolling reduction and annealing time on the fraction of SBs in the Fe-20Cr-19Mn-2Mo-0.82 N high-nitrogen and nickel-free ASS

Fig.2 EBSD-reconstructed images of SBs and random boundaries in the BM: a GBCD of SBs and random boundaries, b GBCD of random boundaries

Fig.3 EBSD-reconstructed images of SBs and random boundaries under different GBE treatment conditions: a and b r3%-a1423K/72 h, c and d r5%-a1423K/72 h, e and f r7%-a1423K/72 h, g and h r10%-a1423K/72 h

Fig.4 Optical micrographs of oxalic acid electrolytic corrosion after sensitizing at 1123 K for 2 h in the different samples: a BM, b r5%-a1423K/72 h, c r10%-a1423K/72 h

Fig.5 SEM images of the surfaces in the BM, r10%-a1423K/72 h and r5%-a1423K/72 h samples after 24 h, 48 h and 72 h ferric sulfate-sulfuric acid corrosion tests

Fig.6 SEM images of the cross sections in the BM, r10%-a1423K/72 h and r5%-a1423K/72 h samples after 24 h, 48 h and 72 h ferric sulfate-sulfuric acid corrosion tests

Fig.7 Comparison of weight loss versus corrosion duration curves for the BM, r10%-a1423K/72 h and r5%-a1423K/72 h samples

Fig.8 Comparison of the corrosion rate in the BM, r10%-a1423K/72 h and r5%-a1423K/72 h samples during ferric sulfate-sulfuric acid corrosion tests

Fig.9 Average grain size/grain-cluster size versus fraction of ΣCSL boundaries curves for the BM, r10%-a1423K/72 h and r5%-a1423K/72 h samples

Fig.10 Metallographs after oxalic acid electrolytic corrosion (a, c, e) and the corresponding grain boundary distributions obtained by EBSD (b, d, f) in the r5%-a1423K/72 h sample

Fig.11 Percolation depth vs. fraction of Σ3 boundaries curves for the BM, r10%-a1423K/72 h and r5%-a1423K/72 h samples after 24, 48 and 72 h ferric sulfate-sulfuric acid corrosion tests

Fig.12 Schematic diagram showing the hindering of IGC penetration from surface into the interior by Σ3 boundaries distributed in random boundary network