Microstructure evolution of a nickel-base alloy resistant to high temperature during aging

ALBERTO PICASSO; CÉSAR LANZ; MATÍAS SOSA LISSARRAGUE; ALDO GARÓFOLI

Journal of Minerals and Materials Characterization and Engineering

Scientific Research Publishing

Año: 2016 vol. 4

2327-4077

In the present study, the microstructural evolution during aging at 750, 800, 850 and 900oC of a 35Cr-45Ni heat resistant alloy, produced in the form of centrifugally cast tubes, was characterized by means of light optical microscopy, scanning electron microscopy (SEM) with secondary and backscattered electron imaging, energy-dispersive spectroscopy (EDS) and Vickers hardness tests. The evolution of the Vickers hardness at 750oC for aged samples shows that the microstructure is stable during the analyzed aging period. At 800oC, the rate of increase in hardness is lower than 750oC and this behavior would be associated with morphological changes observed in primary interdendritic carbides and secondary carbides in the matrix. At 850 and 900oC, an atypical behavior in Vickers hardness curve is presented; where it can be seen that at certain aging times, the hardness decreases significantly. A microstructural analysis of these samples indicated that they have a region free of precipitates (near interdendritic edges) where the hardness is lower. Probably, these regions are areas poor in chromium.