Estudo das resistências mecânica e à corrosão e caracterização microestrutural do aço inoxidável 316L fabricado por manufatura aditiva
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Data
2023-04-12
Autores
Cavalcante, Joyce Gomes dos Passos
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A fabricação de ligas metálicas utilizando a manufatura aditiva (MA) é um
processo alternativo que fomenta a inovação no desenvolvimento de novos materiais,
compreendendo a fabricação de produtos mais precisos e com geometrias mais
complexas. Nesse sentido, o aço inox 316L fabricado por MA, em especial, possui alta
resistência à oxidação atmosférica, longa vida útil e possui uma composição com menos
carbono do que os demais, o que previne contra a corrosão intergranular. Este trabalho
propõe o mapeamento da morfologia microestrutural e a avaliação do comportamento
mecânico e de corrosão de amostras de aço inoxidável 316L processadas por manufatura aditiva, empregando a técnica de leito de pó a laser (FLP-L). A caracterização microestrutural das amostras em condições selecionadas foi realizada para entender a evolução das caraterísticas das distâncias entre linhas de varredura com as condições de fabricação. As amostras foram fabricadas utilizando um equipamento modelo Omnisint 160, que conta com laser de itérbio de 500W. Além disso, o material utilizado foi o pó da liga 316L fornecido pela empresa Carpenter. Os ensaios de tração foram realizados utilizando uma máquina modelo Instron 8801. Foram realizados ensaios de espectroscopia de impedância eletroquímica (EIS) e polarização potenciodinâmica. Estes foram feitos em triplicata para garantir a reprodutibilidade dos resultados, usando um potenciostato/galvanostato (GAMRY PCI 450), com eletrólito composto por uma solução Phosphate Buffered Solution (PBS) à temperatura ambiente (25°C). Os ensaios de tração evidenciaram o caráter dúctil do material, com comportamentos lineares semelhantes para todas as condições e limites de escoamento próximos. Ademais, quanto maior a potência do laser utilizado na fabricação das amostras maior foi o valor limite de resistência à tração (tensão última). Em relação aos ensaios de corrosão, após a imersão, pôde-se verificar que, de maneira geral, a resistência à corrosão do aço inoxidável 316L aumenta com o tempo, devido à formação de uma camada protetiva de produto de corrosão. No que tange às imagens aquisitadas por meio de microscópio óptico, notou-se que para a condição de fabricação 1, ou seja, associada a uma menor potência do feixe de laser (147 W), os contornos não estavam tão evidentes quanto nas outras condições de fabricação (184 W e 211 W). Ademais, os resultados das medições mostraram que conforme a potência do feixe de laser foi maior, a distância média entre linhas de varredura aumentou.
The manufacture of metallic alloys using additive manufacturing (AM) is an alternative process that encourages innovation in the development of new materials, including the manufacture of more precise products with more complex geometries. In this sense, the 316L stainless steel manufactured by AM, in particular, has high resistance to atmospheric oxidation, long service life and has a composition with less carbon than others, which prevents intergranular corrosion. This work proposes the mapping of the microstructural morphology and the evaluation of the mechanical and corrosion behavior of 316L stainless steel samples processed by additive manufacturing, using the laser powder bed technique. The microstructural characterization of the samples under selected conditions was carried out to understand the evolution of the characteristics of the distances between scan lines with the manufacturing conditions. The samples were manufactured using an equipment, which has a 500W ytterbium laser. In addition, the material used was 316L stainless steel powder supplied by the company Carpenter. The tensile tests were carried out using an Instron 8801 model machine. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were performed. These were performed in triplicate to ensure the reproducibility of the results, using a potentiostat/galvanostat (GAMRY PCI 450), with an electrolyte consisting of a Phosphate Buffered Solution (PBS) at room temperature (25°C). The tensile tests showed the ductile character of the material, with similar linear behavior for all conditions and close yield strengths. Furthermore, the higher the power of the laser used in the manufacture of the samples, the higher the limit value of tensile strength (ultimate stress). Regarding the corrosion tests, after immersion, it was possible to verify that, in general, the resistance to corrosion of stainless steel 316L increases with time, due to the formation of a protective layer of corrosion product. The micrographs were acquired using an optical microscope, it was noted that for manufacturing condition 1, that is, associated with a lower laser beam power (147 W), the grain contours were not as evident as in the other conditions manufacturing (184 W and 211 W). Furthermore, the measurement results showed that as the laser beam power was higher, the average distance between scan lines increased.
The manufacture of metallic alloys using additive manufacturing (AM) is an alternative process that encourages innovation in the development of new materials, including the manufacture of more precise products with more complex geometries. In this sense, the 316L stainless steel manufactured by AM, in particular, has high resistance to atmospheric oxidation, long service life and has a composition with less carbon than others, which prevents intergranular corrosion. This work proposes the mapping of the microstructural morphology and the evaluation of the mechanical and corrosion behavior of 316L stainless steel samples processed by additive manufacturing, using the laser powder bed technique. The microstructural characterization of the samples under selected conditions was carried out to understand the evolution of the characteristics of the distances between scan lines with the manufacturing conditions. The samples were manufactured using an equipment, which has a 500W ytterbium laser. In addition, the material used was 316L stainless steel powder supplied by the company Carpenter. The tensile tests were carried out using an Instron 8801 model machine. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were performed. These were performed in triplicate to ensure the reproducibility of the results, using a potentiostat/galvanostat (GAMRY PCI 450), with an electrolyte consisting of a Phosphate Buffered Solution (PBS) at room temperature (25°C). The tensile tests showed the ductile character of the material, with similar linear behavior for all conditions and close yield strengths. Furthermore, the higher the power of the laser used in the manufacture of the samples, the higher the limit value of tensile strength (ultimate stress). Regarding the corrosion tests, after immersion, it was possible to verify that, in general, the resistance to corrosion of stainless steel 316L increases with time, due to the formation of a protective layer of corrosion product. The micrographs were acquired using an optical microscope, it was noted that for manufacturing condition 1, that is, associated with a lower laser beam power (147 W), the grain contours were not as evident as in the other conditions manufacturing (184 W and 211 W). Furthermore, the measurement results showed that as the laser beam power was higher, the average distance between scan lines increased.
Descrição
Palavras-chave
Aço Corrosão, Aço inoxidável austenítico, Ligas de níquel, Microestrutura, Propriedades mecânicas