Synthesis, structure, and mechanical properties of Ni–Al and Ni–Cr–Al superalloy foams

Reticulated nickel foams were alloyed with 8–9 wt% Al or 14–18 wt% Cr and 5–9 wt% Al in a three-step method consisting of (i) gas-phase deposition of Cr and/or Al onto the struts of a pure Ni foam by pack-cementation at 1000 C; (ii) homogenization at 1200 C to remove concentration gradients and to solutionize the alloyed struts; (iii) aging at 900 C to form c0 precipitates within the struts. The resulting alloyed foams retain the low relative densities (less than 3%) and open-cell structure with hollow struts of the original pure Ni foams, and they exhibit struts with the c=c0 structure typical of nickel-base superalloys. The compressive behavior of the superalloy foams, measured at ambient temperature, is compared to model predictions. The creep behavior of the superalloy foams, measured between 680 and 825 C in the stress range of 0.1–0.3 MPa, is discussed using two models assuming strut compression or strut bending as deformation modes. 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.