Surface Modification of Nickel Foams by a Slurry Aluminizing Process

Abstract

A novel slurry‐based process for aluminizing nickel foams while improving the mechanical properties and conserving the excellent ductility is reported. Cellular unalloyed nickel foams with 92% porosity and uniform pore size and distribution were used as a starting material. Several slurries of different compositions were examined to investigate the possibility of developing an aluminide‐nickel intermetallic coating on a Ni foam without considerably degrading the original ductile properties of the foam. The process temperature was varying from 400 to 850° C and the process holding time was ranging between 2h to 6h. Scanning electron microscopy with an energy dispersive X‐ray spectrometry and X‐Ray diffraction were applied to assess the effectiveness of the aluminizing process and determine both the optimum parameters of the procedure (slurry composition, holding temperature and time) and the concentration profiles across the coating cross‐section. The mechanical behavior of the aluminized Ni‐foams was evaluated by the conduction of micro‐tension tests. The resulting Ni‐foams after aluminization retain the pore structure of original Ni‐foams and present a thick outer surface layer which consists of a range of aluminide phases. The mechanical properties of the Ni‐foams aluminized in low process temperature were insignificantly affected.