Effect of brief thermal aging on stress corrosion cracking susceptibility of LDSS 2101 in the presence of chloride and thiosulphate ions

Resistance of Thermally Aged DSS 2304 against Localized Corrosion Attack

“…As an example, Figure 10a shows the behaviour of the as-received sample and the samples aged at 850 °C for different times. A similar behaviour was observed on the alloy LDSS 2101, with a nitrogen content of 0.22 wt%, where an increment in ductility of about 40% after 30 min aging at 850 °C was detected, essentially due to a large chromium nitride precipitation [28]. In DSS 2304, the observed formation of ductile γ2 phase under prolonged aging could also have contributed to the εf% increase [43].…”

“…The SCC susceptibility of DSS 2304 was evaluated in standard NACE TM-0177 solution at pH 2.7 and 25 • C, in the presence of S 2 O 3 2− at 10 −3 M, by slow strain rate tests (SSRT). The use of S 2 O 3 2− ions in replacement of H 2 S was discussed in our preceding papers [26][27][28]. Depending on the alloy potential and solution pH, S 2 O 3 2− allows the assessment of the influence of H 2 S on SCC resistance under health-safe testing conditions and at lower costs of experimental setup [29].…”

Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range

“…Mechanical and corrosion properties in duplex stainless steels (DSSs) closely depend on microstructural characteristics including α/γ phase ratio and secondary phase formation during production or welding operations. In particular, in previous works [6][7][8][9][10][11], we found that short-term thermal aging between 650 and 850 • C negatively affected both localized and stress corrosion cracking (SCC) resistance of LDSS 2101 and DSS 2304. In 2101 grade, because of its high N alloyed-content (0.22 wt.%), thermal aging from 5 to 30 min in the 650-850 • C range mainly induced chromium nitride formation at grain boundaries.…”

“…In both alloys, sigma (σ) phase formation was not detected after thermal aging, because of their low Mo concentration (0.3 wt.%), which slowed down the precipitation rate of this deleterious phase [12][13][14]. Precipitation of chromium compounds in the studied alloys led to formation of chromium-depleted areas adjacent to these secondary phases, which stimulated pitting corrosion initiation, induced sensitization to intergranular corrosion (IGC), and also susceptibility to SCC in chloride environments containing thiosulphate ions (S 2 O 3 2− ) [6,8,10]. In particular, the longest thermal aging at 650 and 750 • C resulted most deleterious for the resistance to localized corrosion on both LDSS 2101 and DSS 2304, while generally a recovery of the performances was observed after aging at 850 • C. This effect was due to a rediffusion of chromium from the grain bulk towards the depleted regions at the grain boundaries.…”

“…Starting from the results of previous research studies carried out in our laboratory on LDSS 2101 and DSS 2304 [6][7][8][9][10][11][21][22][23], in this work the effects of brief (5, 10, and 60 min) thermal aging between 650 and 850 • C on the pitting and IGC corrosion behaviors of LDSS 2404 were investigated. With this aim, both electrochemical tests and scanning electron microscope (SEM) observations, coupled to energy-dispersive X-ray spectroscopy analyses (SEM-EDS), were performed also with the help of the focused ion beam coupled to SEM imaging (FIB-SEM) technique.…”