Efficacy of an external chromia layer in reducing nitridation of high temperature alloys
Tommy Sand, Sedigheh Bigdeli, Mohammad Sattari, Jan Andersson, Mats Hättestrand, Thomas Helander, Johan Eklund, J.-E. Svensson, M. Halvarsson, L.-G. Johansson
Abstract
Six high temperature alloys have been exposed in N2/H2 environments at 900 °C. In order to study the efficacy of a chromia barrier layer against nitrogen ingress, experiments were performed in two environments having the same N2/H2 ratio but slightly different water content, chromia formation being spontaneous in one case only. The samples were evaluated by SEM/STEM/EDX, XRD, gravimetry and GD-OES. The presence of an external chromia scale reduced nitridation of the alloy by 50–95%. Furthermore, in the presence of a continuous alumina layer no nitridation of the alloy was detected.
Topics & Concepts
ChromiaAlloyCorrosionMaterials scienceLayer (electronics)MetallurgyNitrogenBarrier layerChemistryComposite materialOrganic chemistryHigh-Temperature Coating BehaviorsCatalytic Processes in Materials ScienceAdvanced ceramic materials synthesis