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

• Autor(a) principal: Campos,Marcelo
• Data de Publicação: 2014
• Outros Autores: Souza,Sylvio Dionysio de, Martinez,Luis Gallego, Olzon-Dionysio,Maristela
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Materials research (São Carlos. Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392014000500024
• topic: AISI 316L stainless steel; plasma nitriding; expanded austenite; layer depth; synchrotron diffraction; magnetic character

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.%.