Microstructure and elevated temperature behavior of a spray-atomized and co-deposited Ni 3Al/SiC/TiB 2 intermetallic matrix composite

Abstract

This paper discusses preliminary results on the microstructure and elevated temperature creep rupture behavior of a spray-atomized and co-deposited Ni 3Al composite reinforced with SiC and TiB 2 particulates. Microstructural studies suggest that SiC reacts extensively with Ni 3Al, leading to the formation of other carbide phases, e.g. Cr 3C 2. A well-defined interfacial reaction zone, consisting of two distinct layers, was observed at the Ni 3Al/TiB 2 interface. The layer I consisted of a chromium segregated Ni 3Ti phase and the diffusion of nickel was suggested to be the rate control step in this interfacial reaction. The layer II was a nickel-rich Al 3Ni-type phase; the formation of it may be related to the decomposition of the TiB 2 and the ensuing diffusion of boron. Regarding the elevated temperature behavior of the hot-extruded materials, the monolithic Ni 3Al exhibited longer creep rupture lifetimes compared with that for the Ni 3Al/SiC/TiB 2 intermetallic matrix composite. This behavior was attributed to the formation of cavities around small carbide particles, resulting from the decomposition of SiC particulates.