Effects of Pt on the High-Temperature Oxidation of Fe-Cr and Fe-Cr-Al Base Alloys

Abstract

The effects of Pt on the isothermal oxidation of Fe-24Cr alloys, Fe-24Cr alloys containing 0.063 and 0.87 mass% Y, and Fe-24Cr-4Al alloys containing 0.07 and 0.5 mass% Y at high temperature have been examined. Each alloy, after being coated with a Pt thin film by the spattering method, was oxidized in flowing O2 gas in the temperature range from 1173 to 1523 K. Pt-coating on the Y-free Fe-24Cr aIloy resulted in a marked suppression in oxidation rate, while a significant enhancement in oxidation rate by Pt-coating was observed in the Y-containing Fe-24Cr alloys. Pt-coating had no influence on the isothermal oxidation of the Y-containing Fe-24Cr-4Al alloys. The effects of Pt on the oxidation behavior of Fe-24Cr alloys and the Y-containing Fe-24Cr alloys were discussed in relation to defect structures of Cr2O3 scales formed on the alloys. Marker studies using a thin Pt-wire were performed on the Y-containing Fe-24Cr alloys at 1423 K and on the Y-containing Fe-24Cr-4Al alloys at 1523 K. It was observed that Pt reacted aggressively with Cr2O3 scales and affected the development of them, while Pt on the α-Al2O3 scales was inert.