A new class of high temperature and corrosion resistant nickel-based open-cell foams

A number of nickel-based (e.g. Inconel) and ironbased (e.g. Incoloy or Fecralloy) alloys have been successfully developed for applications at high service temperatures and in corrosive environments. Applications such as diesel particulate filters, heat exchangers, and catalyst supports require open-cell porous structures with tailored and uniform material and structural properties, a requirement which can be met by high temperature and corrosion resistant metallic alloy foams prepared with compositions similar to those mentioned above. A new technology that transforms pure nickel foam into an alloy foam, and which has now reached the pilot plant production stage, will be introduced. This technique starts from commercially-available nickel foam, which is uniformly coated with a pre-alloyed powder using standard powder metallurgical methods, and subsequently transformed into the desired alloy throughout the strut cross-section in a relatively short time with a carefully controlled heat treatment that utilizes transient liquid phase sintering. This process allows for the preparation of a wide variety of foam compositions and structural features, which is important for tailoring material properties to a specific application. As the physical dimensions of the final alloy foam structure are similar to those of the starting nickel foam, which is available in different pore sizes, it is possible to produce alloy foams over a wide range of pore sizes (i.e. from approx. 300 micrometer to over 2000 micrometer) by this method. In this way, the foam surface, transport, and filtration properties can be widely adapted to the respective applications. An overview of the most promising alloy foams will be given, with respect to sintering behaviour, mechanical properties, and corrosion testing. A specific focus will be to demonstrate the potential of Fe-Ni-Cr-Al foams for use in high temperature applications. Another important aspect that will be covered is the manufacturability of the foams; different product shapes will be shown and their manufacturing will be explained. The discussion of the current applications for these alloy foams will focus on diesel soot filtration with respect to the filtration properties (e.g. back pressure, efficiency, filter design, etc.) of the alloy foams. Entnommen aus TEMA