Artigos
URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/795
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Artigo de evento 1 Citação(ões) na Scopus Pit morphology and its microstructure relation in 850°C aged UNS S31803 (SAP 2205) duplex stainless steel(2003-07-24) Rodrigo Magnabosco; ALONSO-FALLEIROS, N.This work described the relationship between microstructure of UNS S 31803 (SAP 2205) aged at 850°C and pitting morphology after cyclic polarization in chloride aqueous solution. The initial material, solution treated for 30 minutes at 1120°C and water quenched, was aged at 850°C for periods up to 100 hours. Cyclic polarization in 3,5% NaCl aqueous solution was conducted on #600 grounded sample surfaces. After polarization, the samples were sectioned transversal and perpendicular to polarized surface to allow the inner view of pitting corrosion using scanning electron microscope. It was found that sigma phase formation after 850°C aging treatment reduced pitting potential, and pitting corrosion occurred as selective corrosion of chromium and molybdenum impoverished regions, like interfaces between sigma phase and metallic matrix.- Effect of aging heat treatment H950 and H1000 on mechanical and pitting corrosion properties of uns s46500 stainless steel(2018-01-05) BERALDO, C. H.; CALDERON-HERNANDEZ, J. W.; Rodrigo Magnabosco; ALONSO-FALLEIROS, N.© 2018 Universidade Federal de Sao Carlos. All rights reserved.The effect of aging temperature on mechanical and pitting corrosion properties of UNS S46500 was investigated. Tensile and Hardness tests were carried out and the microstructure was analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction; Thermo-Calc simulations helped in the phase identification. Pitting corrosion properties were investigated in 0.6M NaCl electrolyte with sulfate additions by Potentiodynamic Polarization (PP). Hardness, tensile and yield strength of the UNS S46500 steel after lower aging temperature, 510ºC (H950), are higher than the ones found in the 538ºC (H1000) aged steel.This result is explained by microstructure, X-ray diffraction and Thermo-Calc analysis, which indicated the presence of austenite, chi phase and probably Ni3Ti precipitates finely and uniform distributed throughout the martensite matrix. Pitting corrosion resistance is equivalent in both aging temperatures. The sulfate inhibitor effect on UNS S46500 steel was enhanced for 538ºC condition when the electrolyte reaches 1Cl-:1SO4 2- ratio, which is explained by Ni sulfate adsorption and the amount of interfaces in the microstructure resulting in smaller amount of adsorption sites, such as coarsened Ni3Ti precipitates, smaller fraction of chi phase and recovery of dislocations in martensite structure.
- 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.
- Corrosion versus mechanical tests for indirect detection of alpha prime phase in UNS S32520 super duplex stainless steel(2011-04-05) FONTE, T. F.; Rodrigo Magnabosco; TERADA, M.; PADILHA, A. M.; COSTA, I.Alpha prime formation leads to material embrittlement and deterioration of corrosion resistance. In the present study, the mechanical and corrosion behavior of super duplex stainless steel UNS S32520 aged at 475°C from 0.5 h to 1,032 h was evaluated using microhardness measurements, Charpy impact tests, electrochemical impedance spectroscopy, and cyclic polarization curves. The sensibility of these tests to the effects of alpha prime phase was investigated. The microhardness test showed a gradual increase in hardness with aging time, whereas the impact tests revealed losses of about 80% in the energy absorption capacity for the material aged for 12 hin comparison with the solution-annealed samples. The most responsive analysis was the impact test, which indirectly revealed the presence of this deleterious phase in samples aged for 0.5 h. The electrochemical impedance spectroscopy and polarization tests were not highly sensitive to the alpha prime phase unless these are present In large amounts in the stainless steel. © 2011, NACE International.
Artigo Relation Between Pitting Potential and PREN Values for Ferrite and Austenite in Duplex Stainless Steels(2019-12-12) SANTOS, D.C; MACARRAO, I. M.; Rodrigo MagnaboscoThis work aims to investigate the relation between PREN of ferrite and austenite and the pitting potential of UNS S31803 DSS. Samples were solution-treated between 1040 °C and 1150 °C generating different phase fractions and, consequently, different alloy element contents. ThermoCalc® thermodynamic simulations were performed to predict the chemical composition of each phase allowing the PREN calculations. Besides, potentiodynamic polarization tests were conducted in 0.6 M NaCl solution at 70 °C to correlate pitting potential (Epit) and PREN. Thermodynamic simulation reveals that PREN for ferrite is higher than austenite between 975 °C and 1300 °C. Nevertheless, the electrochemical results show a slight reduction of pitting potential with increasing ferrite content, probably related to the reduction of Cr and Mo contents in this phase. Pits were found preferably in ferrite and in ferrite/austenite interfaces. This behavior suggests that, even with only a slight reduction of pitting potential and, consequently, a discrete corrosion resistance reduction, ferrite is more susceptible to pitting. No pits were found in austenite, suggesting that higher N contents are fundamental to maintain the corrosion resistance of this phase.- Relation Between Pitting Potential and PREN Values for Ferrite and Austenite in Duplex Stainless Steels.(2019-12-12) Daniella Caluscio dos Santos ; MACARRÃO, ISABELLE MONFRINATTI; Rodrigo MagnaboscoThis work aims to investigate the relation between PREN of ferrite and austenite and the pitting potential of UNS S31803 DSS. Samples were solution-treated between 1040 °C and 1150 °C generating different phase fractions and, consequently, different alloy element contents. ThermoCalc® thermodynamic simulations were performed to predict the chemical composition of each phase allowing the PREN calculations. Besides, potentiodynamic polarization tests were conducted in 0.6M NaCl solution at 70 °C to correlate pitting potential (Epit) and PREN. Thermodynamic simulation reveals that PREN for ferrite is higher than austenite between 975 °C and 1300 °C. Nevertheless, the electrochemical results show a slight reduction of pitting potential with increasing ferrite content, probably related to the reduction of Cr and Mo contents in this phase. Pits were found preferably in ferrite and in ferrite/austenite interfaces. This behavior suggests that, even with only a slight reduction of pitting potential and, consequently, a discrete corrosion resistance reduction, ferrite is more susceptible to pitting. No pits were found in austenite, suggesting that higher N contents are fundamental to maintain the corrosion resistance of this phase.
- Investigação do efeito do teor de intersticiais sobre o grau de sensitização em aços inoxidáveis ferríticos a 600ºC(2007-05-22) SERNA-GIRARDO, CARLOS AUGUSTO; IDE, CRISTIANE REIS; Rodrigo Magnabosco; KUNIOSHI, CLARICE TERUI; ALONSO-FALLEIROS, NEUSAO objetivo do presente trabalho foi investigar o efeito do teor de carbono e nitrogênio em aços inoxidáveis ferríticos com 17%Cr (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) sobre o grau de sensitização (GS). Os aços foram solubilizados a 1200°C e resfriados em água. Tratamentos isotérmicos foram realizados a 600°C entre 5 minutos e 16 horas. Foi realizado o ensaio de reativação eletroquímica potenciodinâmica de ciclo duplo (DL-EPR) em solução 0,5M H2SO4 a (25 ± 2)°C. O GS foi medido através da relação entre as densidades de correntes anódicas máximas nas etapas de reversão, i r, e ativação, i a. O exame microestrutural dos corpos-de-prova foi realizado nos microscópios óptico e eletrônico de varredura após ataque metalográfico com reagente Vilella. Os resultados mostram variação do GS com o tempo. Um máximo de GS foi obtido para cada aço e, posteriormente, foi observada diminuição do GS. A intensidade do GS e o tempo de ocorrência variaram em função dos teores de carbono e nitrogênio nos aços.
Artigo VIDA EM FADIGA DE AÇOS CARBONO COM ESTRUTURA BIFÁSICA FERRITA-MARTENSITA(2001-10-31) Rodrigo Magnabosco; BOTTON, T.