PSI - Issue 82

S.S.M. Tavares et al. / Procedia Structural Integrity 82 (2026) 192–198 Tavares et al. / Structural Integrity Procedia 00 (2026) 000–000

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specimens, an increase in hardness is expected only after ~ 5-10% of s phase (Gunn, 1997), and this was corroborated by the results of specimens ST-850-15 and ST-850-30. In specimens cold worked and aged, the material undergoes softening by recrystallisation and recovery of g and d phase, and any hardening effect of s and c is hindered. Significant hardening is only observed in specimens with very high amount of intermetallics, as observed in specimen 1100-SC. Linear sweep voltammetry (LSV) can be used to study the deleterious phases giving quantitative (de Sampaio et al., 2023) as well qualitative results. The LSV curves of specimens AR and ST, which do not contain deleterious phases, shows only one peak. When the steel presents intermetallic phases, other peaks appear, as shown in Fig. 5(a,b). These results shows that the small amounts c and s present in specimens AR-850-15, AR-850-30, ST-850-15 and ST 850-30 can be detected by the LSV method.

(a)

(b)

Fig. 5. LSV curves: (a) AR, AR-850-15 and AR-850-30; (b) ST, ST-850-15 and ST-850-30.

4. Conclusions The deleterious phase precipitation and its early detection in UNS S39274 steel was studied. Isothermal aging at 850 o C for 15 minutes in cold worked (as received, AR) and solution treated (ST) specimens provoked intergranular precipitation of the c phase, which caused a significant decrease in impact toughness. The % c measured by quantitative metallography (image analysis) was 1.4% in the specimen as received and aged at 850 o C/15 min., and such a small amount could be detected by ferritoscope analysis and linear sweep voltammetry (LSV) in KOH solution. Acknowledgements The authors acknowledge Conselho Nacional de Desenvolvimento Científico e Tecnológico - Brasil (CNPq 308244/2022-2; 308930/2025-8), Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ E 26/200.525/2025) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil for the scholarship received (CAPES Finance Code 001). References Alvarez-Armas, I., Degallaix-Moreuil, S. (Eds.), 2009. Duplex stainless steels. John Wiley & Sons and ISTE, London : Hoboken. ASTM, 2022. A790/A790M Standard specification for seamless and welded ferritic/austenitic stainless steel pipe. ASTM International, West Conshohocken. Bettini, E., Kivisäkk, U., Leygraf, C., Pan, J., 2014. Study of corrosion behavior of a 2507 super duplex stainless steel: influence of quenched-in and isothermal nitrides. Int. J. Electrochem. Sci. 9, 61–80. https://doi.org/10.1016/S1452-3981(23)07698-8