Potential and limitations of microanalysis SEM techniques to characterize borides in brazed Ni-based superalloys

José Ruiz-Vargas (1, 2) , Nathalie Siredey-Schwaller (1, 3) , Pierre Noyrez (4) , Sandrine Mathieu (4) , P. Bocher (2) , Nathalie Gey (1)

1 LEM3 - Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux
2 ETS - Ecole de Technologie Supérieure [Montréal]
3 Labex DAMAS
4 IJL - Institut Jean Lamour

Brazed Ni-based superalloys containing complex phases of different Boron contents remain difficult to characterize at the micrometer scale. Indeed Boron is a light element difficult to measure precisely. The state-of-the-art microanalysis systems have been tested on a single crystal MC2 based metal brazed with BNi-2 alloy to identify boride precipitates. Effort has been made to evaluate the accuracy in Boron quantitation. Energy-dispersive and wavelength-dispersive X-ray spectroscopy attached to a Scanning Electron Microscope have first been used to determine the elemental composition of Boron-free phases, and then applied to various types of borides. Results have been compared to the ones obtained using a dedicated electron probe microanalysis, considered here as the reference technique. The most accurate method to quantify Boron using EDS is definitely by composition difference. A precision of 5 at.% could be achieved with optimized data acquisition and post-processing schemes. Attempts that aimed at directly quantifying Boron with various standards using EDS or coupled EDS/WDS gave less accurate results. Ultimately, Electron Backscatter Diffraction combined with localized EDS analysis has proved invaluable in conclusively identifying micrometer sized boride precipitates; thus further improving the characterization of brazed Ni-based superalloys.

Mots clés: EBSD; EPMA; EDS; SEM WDS; Ni-based superalloys; Boron quantitation

Domaines: Sciences de l'ingénieur [physics]; Matériaux

José Ruiz-Vargas, Nathalie Siredey-Schwaller, Pierre Noyrez, Sandrine Mathieu, P. Bocher, et al.. Potential and limitations of microanalysis SEM techniques to characterize borides in brazed Ni-based superalloys. Materials Characterization, 2014, 94, pp.46-57. ⟨10.1016/j.matchar.2014.04.009⟩. ⟨hal-01513630⟩