“…From the FFT patterns, it is indicated that the G-phase maintains a cube-to-cube relationship with δ-ferrite. This is in agreement with previous reports on stainless steel welds and duplex stainless steels, attributed to the smaller mismatch in the lattice parameter with ferrite 6 , 8 , 10 , 46 , 47 . Figure 5 HR-TEM micrographs and FFT patterns of δ-ferrite in ER316Lweld ( a ) as-welded condition, ( b ) aged at 400 °C for 20,000 h, and ( c ) R-HT condition.…”
Section: Resultssupporting
confidence: 93%
“…In general, the corrosion resistance has been observed to degrade with the evolution of phase separation over long aging periods, where the Cr-depleted, Fe-rich α phase is more susceptible towards electrochemical dissolution. It is also reported that, the precipitation of other intermetallic phases like G-phase together with the phase separation affects the corrosion resistance 6 – 8 , 10 , 11 , 25 , 34 – 36 , 39 .…”
Section: Introductionmentioning
confidence: 98%
“…Due to spinodal decomposition, the Cr-content in Fe-rich α phase will be depleted significantly, resulting in the degradation of corrosion resistance of δ-ferrite phase. Many researchers have utilized the electrochemical analysis to study the phase separation of ferrite in thermally aged duplex stainless steels 17 – 36 , ferritic stainless steels 37 – 40 and austenitic stainless steel welds 6 – 8 , 10 , 11 . In general, the corrosion resistance has been observed to degrade with the evolution of phase separation over long aging periods, where the Cr-depleted, Fe-rich α phase is more susceptible towards electrochemical dissolution.…”
Section: Introductionmentioning
confidence: 99%
“… 17 observed separate activation/reactivation peaks corresponding to ferrite and austenite phases in a duplex stainless steel containing 65% ferrite content, where the reactivation current density of the ferrite was found to increase with aging time. In the case of austenitic stainless steels containing smaller ferrite fraction, the electrochemical response of ferrite will be completely overlapped with that of austenite in the double-loop electrochemical potentiokinetic reactivation (DL-EPR) analysis, without any indications of ferrite electrochemical response 6 – 8 , 10 , 11 , 19 , 33 . Further, the ferrite remains in the passivation regime at the point where austenite is electrochemically active at higher electrochemical potentials.…”
Section: Introductionmentioning
confidence: 99%
“…To address this concern, we have studied the DL-EPR analysis of δ-ferrite exclusively by selectively etching the austenite matrix. Then, we have compared the electrochemical response of the weld material (termed as bulk material) as used in the reported studies 6 – 8 , 10 , 11 , with that of the δ-ferrite phase only after etching the austenite. Further, we have discussed about the implications of studying the electrochemistry of δ-ferrite phase only compared to the bulk material.…”
Cr-segregation by spinodal decomposition and G-phase precipitation were observed in δ-ferrite of austenitic stainless steel welds thermally aged at 400 °C for up to 20,000 h. A reversion heat treatment (R-HT) at 550 °C for 1 h dissolved the Cr-segregation in the aged welds while some intermetallic precipitates were present. The double-loop electrochemical potentiokinetic reactivation (DL-EPR) analysis showed no significant differences among them. However, after selective etching of the austenite phase, the DL-EPR values of δ-ferrite phase steadily increased with aging time due to the growth of Cr-depleted regions by spinodal decomposition. The electrochemical behavior of δ-ferrite after R-HT condition was similar to that of unaged welds, indicating the intermetallic precipitates did not affect the corrosion resistance in this case. Overall, DL-EPR analysis of δ-ferrite phase provided better correlation with spinodal decomposition.
“…From the FFT patterns, it is indicated that the G-phase maintains a cube-to-cube relationship with δ-ferrite. This is in agreement with previous reports on stainless steel welds and duplex stainless steels, attributed to the smaller mismatch in the lattice parameter with ferrite 6 , 8 , 10 , 46 , 47 . Figure 5 HR-TEM micrographs and FFT patterns of δ-ferrite in ER316Lweld ( a ) as-welded condition, ( b ) aged at 400 °C for 20,000 h, and ( c ) R-HT condition.…”
Section: Resultssupporting
confidence: 93%
“…In general, the corrosion resistance has been observed to degrade with the evolution of phase separation over long aging periods, where the Cr-depleted, Fe-rich α phase is more susceptible towards electrochemical dissolution. It is also reported that, the precipitation of other intermetallic phases like G-phase together with the phase separation affects the corrosion resistance 6 – 8 , 10 , 11 , 25 , 34 – 36 , 39 .…”
Section: Introductionmentioning
confidence: 98%
“…Due to spinodal decomposition, the Cr-content in Fe-rich α phase will be depleted significantly, resulting in the degradation of corrosion resistance of δ-ferrite phase. Many researchers have utilized the electrochemical analysis to study the phase separation of ferrite in thermally aged duplex stainless steels 17 – 36 , ferritic stainless steels 37 – 40 and austenitic stainless steel welds 6 – 8 , 10 , 11 . In general, the corrosion resistance has been observed to degrade with the evolution of phase separation over long aging periods, where the Cr-depleted, Fe-rich α phase is more susceptible towards electrochemical dissolution.…”
Section: Introductionmentioning
confidence: 99%
“… 17 observed separate activation/reactivation peaks corresponding to ferrite and austenite phases in a duplex stainless steel containing 65% ferrite content, where the reactivation current density of the ferrite was found to increase with aging time. In the case of austenitic stainless steels containing smaller ferrite fraction, the electrochemical response of ferrite will be completely overlapped with that of austenite in the double-loop electrochemical potentiokinetic reactivation (DL-EPR) analysis, without any indications of ferrite electrochemical response 6 – 8 , 10 , 11 , 19 , 33 . Further, the ferrite remains in the passivation regime at the point where austenite is electrochemically active at higher electrochemical potentials.…”
Section: Introductionmentioning
confidence: 99%
“…To address this concern, we have studied the DL-EPR analysis of δ-ferrite exclusively by selectively etching the austenite matrix. Then, we have compared the electrochemical response of the weld material (termed as bulk material) as used in the reported studies 6 – 8 , 10 , 11 , with that of the δ-ferrite phase only after etching the austenite. Further, we have discussed about the implications of studying the electrochemistry of δ-ferrite phase only compared to the bulk material.…”
Cr-segregation by spinodal decomposition and G-phase precipitation were observed in δ-ferrite of austenitic stainless steel welds thermally aged at 400 °C for up to 20,000 h. A reversion heat treatment (R-HT) at 550 °C for 1 h dissolved the Cr-segregation in the aged welds while some intermetallic precipitates were present. The double-loop electrochemical potentiokinetic reactivation (DL-EPR) analysis showed no significant differences among them. However, after selective etching of the austenite phase, the DL-EPR values of δ-ferrite phase steadily increased with aging time due to the growth of Cr-depleted regions by spinodal decomposition. The electrochemical behavior of δ-ferrite after R-HT condition was similar to that of unaged welds, indicating the intermetallic precipitates did not affect the corrosion resistance in this case. Overall, DL-EPR analysis of δ-ferrite phase provided better correlation with spinodal decomposition.
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