Creep of Ni-Al and Ni-Cr-Al superalloy foams

The steady-state creep rate of Ni-base metallic foams, with superalloy composition (in wt. pct) Ni-7.8similar to9.1Al (relative density, rho* = 2.5-2.6) and Ni-13.5similar to16.6Cr-5.1similar to8.9Al (rho* = 2.8similar to3.0), was measured under a range of temperatures (680similar to825degreesC) and applied stresses (0.1similar to0.3 MPa), and compared with that of NiAl intermetallic foams (rho* = 5.3). The stress exponent and activation energy are within the expected range for bulk superalloys. At 825degreesC, Ni-Cr-Al foams display creep rates lower by ca. a factor 10 as compared to Ni-Al foams, and higher by ca. a factor 10 as compared to the NiAl intermetallic foams. These differences are discussed in terms of foam density and strut material creep resistance.