Y. Guan et Wf. Gale, Transient liquid phase bonding of a Hf bearing single crystal nickel aluminide to MM247 superalloy, MATER SCI T, 15(2), 1999, pp. 207-212
An investigation of transient liquid phase bonding of single crystal NiAl t
o a conventional polycrystalline nickel base superalloy MM247 is presented
here. The NiAl substrate material employed was cast single crystal NiAl (B2
compound beta phase) with 1.5 at.-% hafnium (Hf) as an alloying element. T
he interlayers employed in the bonds were 50 mu m thick pure copper foils.
Based an investigations employing transmission electron microscopy and scan
ning electron microscopy with energy dispersive X-ray spectrometry: the mic
rostructural changes in the joint region and the adjacent substrates were e
xamined as a function of bonding time at a temperature of 1150 degrees C. T
he results indicated that hafnium as an alloying element in single crystal
NiAl had a strong effect on the microstructure of joints. In particular; at
tention is focused on the formation of Hf bearing phases and the suppressio
n of sigma phase precipitation during bonding. MST/3995.