Oxidation Behavior of Highly Porous Metallic Components

This paper covers a study on the oxidation behavior in air of four materials processed by means of powder metallurgy (PM), in such a manner that their porosity will be high and so they can be used to manufacture anodic supports in solid-oxide fuel cells (SOFC). For this, powders with a Fe base (AISI 430L and Fe22Cr grades) and with Ni base (Ni20Cr and Ni625 grades) have been processed through a novel method specifically designed for this type of applications. The oxidation kinetics of the four materials has been studied during their exposure to high temperature, and the oxides formed both inside and on the samples have been characterized. The protective abilities of the oxides formed depend on the chromium losses during sintering of the outer surface, the oxygen diffusion rate during high-temperature exposure and the irregularities on the morphology caused by the processing method. The results of these studies have allowed to reach the conclusion that, from amongst the materials tested, Fe22Cr exhibits the best behavior in air at 800 degrees C.