Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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4 resultados
Resultados da Pesquisa
- Investigation of the effect of the interstitial content on the degree of sensitization at 600°C in ferritic stainless steels Investigação do efeito do teor de intersticiais sobre o grau de sensitização em aços inoxidáveis ferríticos a 600°C(2007-01-05) SERNA-GIRALDO, C. A.; IDE, C. R.; Rodrigo Magnabosco; KUNIOSHI, C. T.; ALONSO-FALLEIROS, N.The purpose of this work was to investigate the effect of carbon and nitrogen in 17%Cr ferritic stainless steels (16%Cr-0.04%C-0.032%N; 17.2%Cr-0.02%C-0.0062%N; 18.5%Cr-0.008%C-0.0213%N) on the degree of sensitization (DOS). These steels were solution annealed at 1200°C and quenched in water. Isothermal treatments were carried out at 600°C between 5 minutes and 16 hours. The Double Loop Electrochemical Potentiokinetic Reactivation test (DL-EPR) was carried out in a 0.5M H2SO4 solution at (25 ± 2)°C. The DOS was evaluated using a ratio between maximum anodic current density in reversion, ir and activation, ia. The microstructural examination of specimens was carried out using optical and scanning electron microscopy after metallographic etching with Vilella's reagent. The results showed a DOS variation with time. Maximum values of DOS were obtained for each steel, followed by its reduction. The intensity of DOS and its kinetics vary in function of the carbon and nitrogen content in steels.
- Relation between pitting potential, degree of sensitization, and reversed austenite in a supermartensitic stainless steel(2017) Calderon-Hernandez J.W.; Hincapie-Ladino D.; Filho E.B.M.; Magnabosco R.; Alonso-Falleiros N.© 2017, NACE InternationalPitting potential (Ep) and degree of sensitization (DOS) of a supermartensitic stainless steel (SMSS) were determined on specimens heat-treated at different tempering temperatures (550°C, 575°C, 600°C, 625°C, 650°C, or 700°C). The effect of pH (pH 6 and pH 8) on the Ep obtained in a 3.5 wt% NaCl solution, as well as the correlation between Ep and DOS obtained in 0.5 M H2SO4 + 0.01 M KSCN solution, was studied. The results showed correlation between Ep and DOS values, the samples with the higher DOS values being the ones with the lower Ep. A mechanism was proposed that would explain the correlation of the presence of reversed austenite formed during tempering, Ep, and DOS.
- Evaluation of microstructural effects on the degree of sensitization (DOS) of a UNS S31803 duplex stainless steel aged at 475°C(2015) De Melo E.B.; Magnabosco R.© 2015, NACE International.In this study, microstructural and electrochemical behavior of a UNS S31803 duplex stainless steel aged at 475°C were investigated. Hardness values increased with aging at 475°C and evidence of alpha prime (α′) phase formation was confirmed by transmission electron microscopy analysis. Double loop electrochemical potentiokinetic reactivation measurements in a 2 M H2SO4 + 0.5 M NaCl + 0.01 M KSCN solution showed an increase in the degree of sensitization values, mainly for the sample aged for 360 h at 475°C. Moreover, the results suggest that α′ phase formation occurred via spinodal decomposition mechanism.
- Sensitization and pitting corrosion resistance of ferritic stainless steel aged at 800°C(2006) Paroni A.S.M.; Alonso-Falleiros N.; Magnabosco R.This work investigates the influence of sensitization conditions on pitting corrosion resistance of ferritic stainless steel UNS S43000 aged at 800°C between 10 min and 320 min. UNS S43000 steel is susceptible to intergranular corrosion after solution treatment at 1,160°C followed by water-quenching, as a consequence of the chromium depletion of the grain boundaries adjacent areas, due to chromium carbide precipitation during cooling. Isothermal treatments of 10 min at 800°C decrease the sensitization degree, and intergranular corrosion resistance is recovered after 20 min at 800°C. The solution-treated specimens have a high pitting potential in 3.5% sodium chloride (NaCl) solution compared to the same material treated at 800°C for 10 min. The resistance to pitting corrosion is reduced by chromium depletion associated with an increase of inter- and intragranular precipitation of chromium carbide. For treatments longer than 20 min at 800°C, the pitting corrosion resistance returns to the high level observed for the solution-treated condition, as a consequence of chromium redistribution that occurs after 20 min at 800°C. The scan rate used in potentiodynamic tests plays a minor role on the pitting potential, while a rougher surface leads to lower pitting potentials in all studied conditions. © 2006, NACE International.