Nickel-based foams for exhaust after treatment components

Abstract

Metallic foams with their specific structural properties are attractive candidates for exhaust after treatment systems, e.g diesel particulate filters (DPF) and catalyst supports. The high temperature and corrosive operating conditions require outstanding material properties. For such applications a number of corrosion resistant nickel- and iron-nickel-based alloys were successfully developed. The paper reports on a powder metallurgical route which transforms a commercial available nickel foam into a high temperature stable foam alloy using a pre-alloyed powder which is coated on the foam substrate and subsequently sintered. A further heat treatment process was developed to enhance the durability over the lifetime. The thermal conditions under an atmosphere with a specific oxygen partial pressure ensure a selective oxidation to form a a- alumina layer which acts as a diffusion barrier to prevent the wash coat aging and furthermore increases the high temperature oxidation resistance considerably