Microstructure, oxidation resistance and tensile properties of silicide coated Nb-alloy C-103

A Fe-Cr-alloyed silicide coating has been formed on a commercially available Nb-alloy called C-103 by using a slurry-based technique followed by vacuum diffusion treatment at 1380 °C. The coating microstructure reveals a three-layer structure with the outer layer consisting of NbSi2 phase and the inner interdiffusion layer consisting of lower silicides such as Nb5Si3 and Nb3Si. The intermediate layer of the coating is comprised of a Fe-Cr alloyed Nb-silicide phase and NbSi2. The coating provides good short-term protection to the substrate against high temperature oxidation in air at 1100 and 1300 °C. It is found that the presence of the coating increases the tensile strength of the alloy.