Navegando por Palavras-chave "stainless steel"
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- ItemAcesso aberto (Open Access)Electrochemical Study of the AISI 409 Ferritic Stainless Steel: Passive Film Stability and Pitting Nucleation and Growth(Univ Fed Sao Carlos, Dept Engenharia Materials, 2017) de Souza, Juliana Sarango [UNIFESP]; de Oliveira, Leandro Antonio; Sayeg, Isaac Jamil; Antunes, Renato AltobelliThe aim of the present work was to study the passive film stability and pitting corrosion behavior of the AISI 409 stainless steel. The electrochemical tests were carried out in 0.1 M NaCl solution at room temperature. The general electrochemical behavior was assessed using electrochemical impedance spectroscopy (EIS) measurements whereas the semiconducting properties of the passive film were evaluated by the Mott-Schottky approach. Pitting corrosion was investigated using potentiodynamic and potentiostatic polarization tests. Surface morphology was examined using confocal laser scanning microscopy and scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy (EDS) analyses were carried out to identify the composition of precipitates that could act as preferential sites for the onset of pitting corrosion. The results showed that the passive film presents n-type semiconductive behavior. Grain boundaries played an important role as pitting initiation sites for the AISI 409 stainless steel.
- ItemSomente MetadadadosEstudo das condições de deposição de filmes finos da liga intermetálica fealcr sobre aço inoxidável austenítico por magnetron sputtering para aplicação em biomateriais(Universidade Federal de São Paulo (UNIFESP), 2015-02-26) Neves, Douglas Valentim Fernandes [UNIFESP]; Cardoso, Kátia Regina Cardoso [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The 316 type austenitic stainless steel (316 SS) is one of the most used metallic materials in medical applications due to the combination of mechanical properties with low cost, compared with other metallic material used for implants. However, wear and corrosion behavior stimulate permanent changes in human tissue that can lead to implant loss. The development of stable and biocompatible coatings presenting suitable mechanical properties and which does not undergo cracking or to peel off during the use is a very promising solution for improving the performance of SS 316 as biomaterials for implants. The objective of this project was to develop a coating based on the FeAlCr intermetallic alloy, which has great potential to be used as biomaterial, on medical grade austenitic stainless steel. The films were obtained by the magnetron sputtering technique. This research aimed to study the effects of electric potential and deposition temperature on adhesion, thickness, roughness and composition of films. The results indicate that the deposition rate and therefore the film thickness increased with the plasma power and the substrate temperature. The films obtained in all the process conditions used are crystalline and have the same chemical composition as the target material. The films showed good adhesion to the substrate and the best results were obtained for the depositions carried out with power 100 W and substrate heated to 300ºC.
- ItemAcesso aberto (Open Access)Porous stainless steel for biomedical applications(ABM, ABC, ABPol, 2011-01-01) Mariotto, Sabrina de Fátima Ferreira; Guido, Vanessa; Yao Cho, Liu; Soares, Cristina Pacheco; Cardoso, Kátia Regina [UNIFESP]; Universidade do Vale do Paraíba Instituto de Pesquisa e Desenvolvimento; Universidade Federal de São Paulo (UNIFESP)Porous 316L austenitic stainless steel was synthesized by powder metallurgy with relative density of 0.50 and 0.30 using 15 and 30 wt. (%) respectively of ammonium carbonate and ammonium bicarbonate as foaming agents. The powders were mixed in a planetary ball mill at 60 rpm for 10 minutes. The samples were uniaxially pressed at 287 MPa and subsequently vacuum heat treated in two stages, the first one at 200 ºC for 5 hours to decompose the carbonate and the second one at 1150 ºC for 2 hours to sinter the steel. The sintered samples had a close porous structure and a multimodal pore size distribution that varied with the foaming agent and its concentration. The samples obtained by addition of 30 wt. (%) of foaming agents had a more homogeneous porous structure than that obtained with 15 wt. (%). The MTT cytotoxicity test (3-[4,5-dimethylthiazol]-2,5-diphenyltetrazolium bromide) was used to evaluate the mitochondrial activity of L929 cells with samples for periods of 24, 48, and 72 hours. The cytotoxicity test showed that the steel foams were not toxic to fibroblast culture. The sample with the best cellular growth, therefore the most suitable for biomedical applications among those studied in this work, was produced with 30 wt. (%) ammonium carbonate. In this sample, cell development was observed after 48 hours of incubation, and there was adhesion and spreading on the material after 72 hours. Electrochemical experiments using a chloride-containing medium were performed on steel foams and compared to massive steel. The massive steel had a better corrosion performance than the foams as the porosity contributes to increase the surface area exposed to the corrosive medium.