High-temperature oxidation behaviour of base material and laser-weld specimens of a thin FeCrAl-RE foil at around 900°C

Abstract

High Temperature Corrosion and Protection of Materials 6 Les Embiez (France) 16-21 mai 2004 ed. P. Steinmetz, I.G. Wright, G. Meier et al... Trans Tech PublicationsInternational audienceIsothermal oxidation of laser welded FeCrAl-RE samples containing specific fractions of seams in a bead-on-plate "configuration" has been performed at around 900°C and studied using TGA, SEM, TEM and EPMA techniques. An important reduction in the alumina-growth rate on the fusion zone occurs at 900°C, thereby, suppressing the discontinuous increase in mass gain commonly observed during the high temperature oxidation of alumina-forming alloys. This phenomenon is mainly related to the concomitant dramatic chromium carbide precipitation at the fusion zone/scale interface and possible earlier injection of the rare earth elements into the scale. The former, which is linked to the laser melting-induced high free carbon, contributes to the increase in effectiveness of the diffusion barrier provided by the thermally growing scale. The latter is correlated with the initial high Ce+La enrichment at the fusion zone surfaces and is manifested by the elimination of detrimental platelet transformation during the initial stages of oxidation