The application of a novel Ni-Cr-Si coating on Fe-9Cr steel for sofc interconnects

In this work, the advantage of applying surface modification techniques, in order to develop high performance materials at a lower cost, and the usefulness of using Cr-Si as corrosion resistant elements for interconnects in SOFC has been demonstrated. A two-steps coating process has been developed on a T91 steel (9Cr-1Mo), in order to grow a high temperature corrosion resistant layer with low electrical resistivity. The coating is composed of two layers. The bi-layer coating was formed by applying a Cr-Si diffusion coating, by pack cementation technique, followed by Ni electroplating. After oxidation at 800°C for 9 days a dense three-layers scale was observed which was composed of a Fe-Ni spinel at the surface, NiO as an intermediate layer, and Cr and Si oxides as the innermost layer. The Fe-Ni spinel and NiO have shown high electrical conductivity. The thickness of this oxide layer was around 5 times lower than an oxide layer grown on Ni plated T91 steel, under the same oxidation conditions. On the other hand, the scale formed on Ni plated T91 steel was highly porous and was not adhered to the substrate. Copyright © 2007 MS&T'07®.