Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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5 resultados
Resultados da Pesquisa
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.Artigo de evento 0 Citação(ões) na Scopus UNS S31803 stainless steel phase transformations during 475°C and 650°C aging and its influence on the pitting potencial in a 0.6M NaCl solution(2010-07-26) MELO, E. B. DE; Rodrigo MagnaboscoThis work evaluates the phase transformations during aging at 475°C or 650°C of UNS S31803 duplex stainless steel and its influence on the pitting potential in a 0.6M NaCl solution. The material was solution treated at 1175°C and water quenched, and then aged at 475°C or 650°C for times up to 360h. Samples were a nalyzed by optical microscopy through quantitative metallography, and ferrite quantification was conducted with a ferritscope. Vickers microhardness measurements were also performed. Cyclic polarization tests were then conducted in a 0.6M NaCl solution, at a scan rate of 1 mV/s. It is found that aging at 475°C leads to a continuous increasing of material microhardness, probably related to the presence of alpha prime phase, and reduction in the pitting potentials were observed for samples aged for more than 12 h. Samples aged at 650°C show the presence of sigma and chi phases, which increased with aging time, and pitting potential is reduced for aging times greater than 4h. The pitting potential reduction in the aged samples is probably associated with the presence of ferrite and/or austenite impoverished in Cr and Mo, as a result of alpha prime formation at 475°C or sigma and chi formation at 650°C.Artigo de evento 0 Citação(ões) na Scopus Influenzce of the sigma phase formation in pitting potential of UNS s31803 duplex stainless steel in 0,6M NACL AGED at 850 E 900°C(2010-07-26) Daniella Caluscio dos Santos; Rodrigo MagnaboscoThe main purpose of this work is to analyze the mechanisms and kinetics of sigma phase formation of UNS S31803 stainless steel after isothermal aging between 850 e 900°C, evaluating the influence of sigma phase formation on pitting potential in 0.6M NaCl solution. Solution treated samples of the UNS S31803 duplex stainless steel were isotermically aged at 850°C or 900°C up to 360 h. The microstructural characterization of the samples was made through quantitative metallography, ferritscope analysis and Vickers microhardness. The cyclic polarization tests used to the determination of the pitting potential were conducted in polished samples. The electrochemical behavior of aged UNS S31803 duplex stainless steel in 0.6M NaCl solution is strongly dependent on the microstructure, since both changes in mechanisms and kinetics of sigma phase formation influenced the pitting potential of the material. Increasing aging time lead to the decrease of pitting potential, due to the formation of chromium impoverished regions. Oscillations in pitting potential values were noted due to the chromium redistribution enabled by easy diffusion of this element in high temperatures.Artigo de evento 0 Citação(ões) na Scopus Ferrite-to-austenite transformation during cold working of a duplex stainless steel(2011-09-23) Rodrigo Magnabosco; TAVARES, D. B.; FORGAS, A.; DE MOURA NETO, C.Ferrite-austenite duplex stainless steels (DSS) are replacing austenitic stainless steels in many applications due to its high mechanical and corrosion resistance. However, magnetic measurements of ferrite volume fraction using a ferritscope of cold worked samples indicate a reduction in the ferrite content with increasing mechanical work. Considering this fact, this work studies the influence of the cold working on the ferrite/austenite ratio. Samples of UNS S31803 DSS sheet, originally 3 mm thick, were solution-treated at 1175°C for 30 minutes and water quenched; after that, different levels of cold working were applied. Ferrite volume fraction was determined using two distinct methods: quantitative stereology with an optical microscope and magnetic measurements using a ferritscope; a detailed microstructural characterization, including X-ray diffractometry, was conducted to base the discussion of a possible ferrite-to-austenite diffusionless transformation.Artigo de evento 3 Citação(ões) na Scopus Comparative study of ferrite quantification methods applied to duplex stainless steels(2011-09-23) Rodrigo Magnabosco; SPOMBERG, S.Duplex stainless steels (DSS) present approximately the same quantities of ferrite (magnetic phase) and austenite. These steels are replacing austenitic stainless steels in some applications due to its high mechanical and corrosion resistance. However, changes in the volumetric percentage of those phases can modify material properties, justifying the development of this study, which has as principal aim a comparison between three different ferrite quantification methods. Samples of two different DSS (UNS S31803 or UNS S32750), originally supplied as 20mm round bars, were solution-treated between 1000°C and 1250°C, in order to obtain different ferrite/austenite ratios. Ferrite quantification was performed in three sections: longitudinal, transverse and diagonally oriented to the rolling direction. The volume fraction of ferrite was determined using three distinct methods: quantitative stereology with an optical microscope, magnetic measurements using a ferritscope, and X-ray analysis by comparison of the relative intensities of peaks corresponding to the planes that generate maximum intensity of diffraction for single-phase samples. Results are discussed, analysing the reliability of the studied methods.