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1. Francisco Evaristo UchÃa Reis. Evaluation of mechanical properties and corrosion resistance in stainless steel model 25Cr 6Mo 5Ni alloy with and without Boron addition.

Degree: PhD, 2015, Universidade Federal do Ceará

Superferritic stainless steels are widely used in heat exchangers and in petrochemical power plant because of their excellent mechanical properties coupled to corrosion resistance in chloride rich environments. In this research new superferritic alloys with high Cr, Mo, and Ni contents were produced for oil industry applications. Therefore, two superferritic stainless steels model alloys were developed, one with 0.07% B addition and another one without this alloying element. The phase diagrams for both materials were carried out by Thermo-Calc computacional program. Microstructure characterization was performed using the following techniques: optical and scanning electron microscopy, energy-dispersive spectroscopy, and Xray diffraction. The mechanical properties were assessed by hardness measurements, Charpy impacts and tensile tests. Corrosion resistance of the model alloys in aqueous solution 0.6 M NaCl was investigated by open circuit potential, potentiodynamic cyclic anodic polarization, and electrochemical impedance spectroscopy. Furthermore, critical pitting temperature was determined. The results showed that the superferritic stainless steel model alloy without B addition achieved better mechanical properties than the one of the two commercial superferritic stainless steels alloys. The corrosion resistance of this alloy was similar to the one of the superaustenitic stainless steels, and superduplex in aqueous solution 0.6 M NaCl. However, there was the formation of eutectoid lamellar constituent like perlite for the superferritic stainless steel model alloy with B addition. This eutectoid constituent was deleterious to mechanical properties, as well as to corrosion resistance for the material developed and studied in this thesis.

Os aÃos inoxidÃveis superferrÃticos sÃo amplamente utilizados em trocadores de calor e em plantas petroquÃmicas, devido a suas excelentes propriedades mecÃnicas associadas à resistÃncia à corrosÃo em ambientes ricos em cloreto. Nesta pesquisa foram produzidas novas ligas superferrÃticas com elevados teores de Cr, Mo e Ni para aplicaÃÃo em plantas petrolÃferas. Portanto, foram desenvolvidas duas ligas modelo de aÃo inoxidÃvel superferrÃtico, uma com 0,07% de B e outra sem adiÃÃo deste elemento de liga. Os diagramas de fases para os materiais foram construÃdos a partir do programa computacional Thermo-Calc. A caracterizaÃÃo microestrutural foi realizada usando as tÃcnicas; microscopia Ãptica, microscopia eletrÃnica de varredura, espectroscopia de energia dispersiva de raios-X e difraÃÃo de raios-X. As propriedades mecÃnicas foram avaliadas por medidas de dureza, ensaios de impacto Charpy e ensaios de traÃÃo. A resistÃncia à corrosÃo das ligas modelo, em soluÃÃo aquosa de 0,6M NaCl, foi avaliada por monitoramento do potencial de circuito aberto, polarizaÃÃo potenciodinÃmica cÃclica e espectroscopia de impedÃncia eletroquÃmica. AlÃm de determinar a temperatura crÃtica de pite. Os resultados obtidos demonstram que, a liga modelo de aÃo inoxidÃvel superferrÃtico sem boro apresentou…

Advisors/Committee Members: Pedro de Lima Neto, Marcelo Josà Gomes da Silva, Juan Manuel Pardal, SÃrgio Souto Maior Tavares, Hamilton Ferreira Gomes de Abreu.

Subjects/Keywords: ENGENHARIA DE MATERIAIS E METALURGICA; SuperferrÃticos; Testes mecÃnicos; Ensaios eletroquÃmicos; CorrosÃo por pite; Superferritic; Mechanical tests; Electrochemical tests; Piting corrosion; CiÃncia dos materiais

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Reis, F. E. U. (2015). Evaluation of mechanical properties and corrosion resistance in stainless steel model 25Cr 6Mo 5Ni alloy with and without Boron addition. (Doctoral Dissertation). Universidade Federal do Ceará. Retrieved from http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15780 ;

Chicago Manual of Style (16th Edition):

Reis, Francisco Evaristo UchÃa. “Evaluation of mechanical properties and corrosion resistance in stainless steel model 25Cr 6Mo 5Ni alloy with and without Boron addition.” 2015. Doctoral Dissertation, Universidade Federal do Ceará. Accessed January 26, 2020. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15780 ;.

MLA Handbook (7th Edition):

Reis, Francisco Evaristo UchÃa. “Evaluation of mechanical properties and corrosion resistance in stainless steel model 25Cr 6Mo 5Ni alloy with and without Boron addition.” 2015. Web. 26 Jan 2020.

Vancouver:

Reis FEU. Evaluation of mechanical properties and corrosion resistance in stainless steel model 25Cr 6Mo 5Ni alloy with and without Boron addition. [Internet] [Doctoral dissertation]. Universidade Federal do Ceará 2015. [cited 2020 Jan 26]. Available from: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15780 ;.

Council of Science Editors:

Reis FEU. Evaluation of mechanical properties and corrosion resistance in stainless steel model 25Cr 6Mo 5Ni alloy with and without Boron addition. [Doctoral Dissertation]. Universidade Federal do Ceará 2015. Available from: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15780 ;

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