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Study of expanded austenite formed in plasma nitrided AISI 316L samples, using synchrotron radiation diffraction

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Resumo:AISI 316L stainless steel samples nitrided at different conditions of temperature and time, showing different properties, such as nitrogen concentration (C N) and nitrided layer thickness, were studied. Expanded austenite (γN) diffraction peaks up to the (222) reflection were observed using suitable wavelength synchrotron radiation. XRD patterns were fitted by Le Bail method, using a special triclinic crystal structure (with a lattice distortion n) for γN, whose peaks were decomposed in a few subpeaks, to consider C N gradient across the nitrided layer. Our results indicate that regarding γN magnetic behavior, which was observed for the samples nitrided at 450 °C, it seems to be correlated not only to high C N (≥31at.%), but also to higher η (≥2.4°), which reaches up to 5.6°. This distortion h decreases when C N increases, consequently, with its minimum close to the surface. On the other hand, for paramagnetic samples (350 °C),η increases up to 1.4° when C N increases up to 30 at.%.
Autores principais:Campos,Marcelo
Outros Autores:Souza,Sylvio Dionysio de; Martinez,Luis Gallego; Olzon-Dionysio,Maristela
Assunto:AISI 316L stainless steel plasma nitriding expanded austenite layer depth synchrotron diffraction magnetic character
Ano:2014
País:Brasil
Tipo de documento:artigo
Tipo de acesso:acesso aberto
Instituição associada:IBICT
Idioma:inglês
Origem:Oasisbr
Descrição
Resumo:AISI 316L stainless steel samples nitrided at different conditions of temperature and time, showing different properties, such as nitrogen concentration (C N) and nitrided layer thickness, were studied. Expanded austenite (γN) diffraction peaks up to the (222) reflection were observed using suitable wavelength synchrotron radiation. XRD patterns were fitted by Le Bail method, using a special triclinic crystal structure (with a lattice distortion n) for γN, whose peaks were decomposed in a few subpeaks, to consider C N gradient across the nitrided layer. Our results indicate that regarding γN magnetic behavior, which was observed for the samples nitrided at 450 °C, it seems to be correlated not only to high C N (≥31at.%), but also to higher η (≥2.4°), which reaches up to 5.6°. This distortion h decreases when C N increases, consequently, with its minimum close to the surface. On the other hand, for paramagnetic samples (350 °C),η increases up to 1.4° when C N increases up to 30 at.%.

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