info:eu-repo/semantics/article
Study of the Microstructural Evolution in a 35Ni-25Cr-Nb Heat-Resistant Alloy by Dilatometry and Electron Microscopy
Fecha
2018-06Registro en:
Sosa Lissarrague, Matías Humberto; Limandri, Silvina Paola; Prado, Fernando Daniel; Picasso, Alberto Carlos; Study of the Microstructural Evolution in a 35Ni-25Cr-Nb Heat-Resistant Alloy by Dilatometry and Electron Microscopy; Springer; Metallography, Microstructure, and Analysis; 7; 3; 6-2018; 356-362
2192-9262
2192-9270
CONICET Digital
CONICET
Autor
Sosa Lissarrague, Matías Humberto
Limandri, Silvina Paola
Prado, Fernando Daniel
Picasso, Alberto Carlos
Resumen
The dendritic-type microstructure of the 35Ni-25Cr-Nb alloy, in the as-cast condition, consists of an austenitic matrix and two types of eutectic primary carbides; Nb-rich MC type and Cr-rich M23C6 type both present in interdendritic edges and grain boundaries. During aging at 1073 K for different times, M23C6-type secondary carbides precipitate in the matrix while MC-type carbides would transform into a Ni-Nb silicide, known as G-phase (Ni16Nb6Si7). The microstructure of this alloy was characterized by scanning electron microscopy with X-ray mapping, backscattered and secondary electron images, electron backscatter diffraction, and dilatometry, in order to detect the G-phase and analyze the conditions under which it is present. This undesirable silicide could reduce creep strength since Nb-rich carbide to G-phase transformation improves nucleation of microcracks in the interface between matrix and the silicide. Silicon and nickel were found on the edges of primary Nb-rich carbides in the as-cast condition. This could be indicating that the transformation of this carbide into Ni-Nb silicide is in an incipient stage and it probably occurs from the outside to the inside of the Nb carbide.