Reduced area specific resistance for iron-based metallic interconnects by surface oxide coatings

The effects of various reactive-element coatings on the oxidation kinetics of two commercial iron-based alloys, Ebrite and ANSI 446, at elevated tempe ratures were investigated. Although NiO is not regarded as a reactive eleme nt oxide, it was chosen as a coating due to the enhanced conductivity of Cr 2O3 by doping with NiO, Hot-dipping was used to make the desired coatings. The results consistently show a pronounced reduction in oxidation rate by e ither a Y2O3 coating or an equally mixed Y2O3/NiO double coating, particula rly at low temperature, but only a slight influence by NiO coating. Examina tion of the scale microstructures revealed a continuous denser scale strong ly bonded to the underlying metal for a Y2O3 coating, but visible micro-cra cks for NiO coating. Electrical resistance measurements after a Y2O3 coatin g indicate a corresponding reduction in area specific resistance (ASR) with platinum and oxide electrodes, but an increase in ASR with oxide electrode s for a NiO coating. With a Y2O3/NiO double coating, a careful control of t he NiO level in the scale has led to a denser, thinner and conducting Cr2O3 scale. (C) 2001 Elsevier Science Ltd. All rights reserved.