Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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4 resultados
Resultados da Pesquisa
- Electrochemical characterization of 13Cr low-carbon martensitic stainless steel - Corrosion study with a mini-cell setup(2022-10-27) CALDERON- HERNANDEZ, J. W.; GONZALEZ-RAMIREZ, M. F.; SEPULVEDA-CASTANO, J. M.; SANTOS-MARTINEZ, J. D.; QUISPE-AVILES, J. M.; Rodrigo Magnabosco; Goldenstein H.© 2022 The Authors.13Cr low-carbon martensitic stainless steels also known as supermartensitic stainless steels (SMSS) have superior properties than conventional martensitic stainless steels. The SMSS have better weldability and corrosion resistance. Nevertheless, corrosion resistance depends on phases transformations which are induced generally by heat treatments. In this work, the electrochemical properties of a SMSS were evaluated as a function of the tempering temperature (400 °C-700 °C). The susceptibility to intergranular corrosion was determined throught the degree of sensitization (DOS) using the Double Loop - Electrochemical Potentiokinetic Reactivation technique (DL-EPR) in a conventional three electrodes corrosion cell. On the other hand, the pitting susceptibility was evaluated by potentiodynamic polarization using a homemade corrosion mini-cell (based on a sessile electrolyte droplet), thus avoiding crevice problems typically seen with conventional arrangements. Imaging the microstructure with SEM, XRD analysis and thermodynamic and kinetic simulations were performed to understand the microstructural transformations and their relationship with corrosion resistance. The most severe sensitization occurs at the temperature where reversed austenite transformation is highest.
- 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.
- Effect of Niobium on Phase Transformations, Mechanical Properties and Corrosion of Supermartensitic Stainless Steel(2017) de Oliveira M.P.; Calderon-Hernandez J.W.; Magnabosco R.; Hincapie-Ladino D.; Alonso-Falleiros N.© 2017, ASM International.The influence of niobium addition in a supermartensitic stainless steel with 13Cr-5Ni-2Mo has been studied. The steel with Nb tempered at 600 °C for 2 h showed improved mechanical resistance properties and lower degree of sensitization, without compromising elongation and pitting corrosion resistance, when compared to the reference steel. In order to understand the Nb effect in such steel, mainly regarding phase transformation, different tempering time intervals have been studied. The better performance of the SM2MoNb is attributed to the hindering effect that Nb has in the kinetics of the phase transformations during tempering, delaying the precipitation start and coarsening stages of the present phases.
- Influence of the microstructure on the degree of sensitization of a duplex stainless steel UNS S31803 aged at 650°C(2013) De Melo E.B.; Magnabosco R.; De Moura Neto C.This work evaluates the phase transformations during aging of an UNS S31803 DSS at 650°C and its influence on the DOS. The material was solution treated at 1175°C and then aged at 650°C for times up to 360 h. SEM-BSC images indicate the formation of Cr2N, σ and ÷ phases in the samples aged at 650°C. The analysis of DL-EPR curves, obtained in a 1 M H2SO4 + 0.25 M NaCl + 0.01 M KSCN solution, shows an increase in DOS values for samples aged at 650°C. Probably, this increase observed in DOS values is mainly related to the presence of Cr-and/or Mo-depleted á, as a result of σ phase, ÷ phase and/or Cr2N formation at 650°C. Moreover, a possible healing up of Cr-and/ or Mo-depleted areas is observed between 1 h and 4 h of aging at 650°C.