Isothermal oxidation behavior and growth kinetics of silicide coatings formed on Nb–1Zr–0.1C alloy

• NbSi2 and double layer (NbSi2 + Nb5Si3) coatings were prepared on Nb–1Zr–0.1C alloy.
• Single layer (NbSi2) coatings showed lower isothermal weight gain during oxidation.
• Amorphous silica scale embedded with Nb2O5 particles is observed after oxidation.
• Kinetic model for the pack siliconizing process has been established.

Isothermal oxidation behavior of the single layer NbSi2 and the double layered (NbSi2 + Nb5Si3) silicide coated Nb–1Zr–0.1C (wt.%) alloys has been studied between 800 and 1300 °C in static laboratory air. The single layer coated alloy shows a lower weight gain as compared to the double layer coatings at all temperatures. The formation of amorphous silica scale embedded with Nb2O5 oxide particles is observed beyond 1100 °C, and a superior oxidation resistance is detected between 1100 and 1300 °C. A kinetic equation relating the thickness of the coating layer with the various process parameters for pack siliconizing of Nb-alloy has been established.