Effects of Zr Distribution on High‐Temperature Oxidation Resistance of a FeCrAlZr Alloy

Abstract

Two FeCrAlZr alloys are fabricated by twin‐roll strip casting (TRSC) and ingot casting (IC), and different Zr distributions are formed. After cyclic oxidation tests at 1200 °C for 200 h in air, it is found that the scale spallation resistance in the FeCrAlZr alloy is improved by homogenizing the Zr distribution by TRSC. To understand the improvement in oxidation resistance, the composition and microstructure of the thermally grown scales are investigated. During oxidation, Zr diffuses toward the scale and forms ZrO2 particles in the scale and at the surface of the oxide scale. Meanwhile, the outward diffusion of Zr inhibits the formation of interfacial voids and S segregation regardless of Zr distribution. However, the TRSC sample with a more uniform Zr distribution can form the high‐density oxide penetrations, keying the scale to the matrix and improving scale adhesion. The Zr fluxes toward the scales are calculated to explain the difference in the distribution of oxide penetrations in the TRSC and IC samples during oxidation.

The Effect of Zr on the High‐Temperature Oxidation Resistance of 12Cr Ferritic/Martensitic Steels

“…As previous thermodynamic analysis, in the oxidation process, Zr in steels is preferentially oxidized to ZrO 2 particles. [ 37 ] The ZrO 2 particles exhibit a high melting point of up to 2983 K and have excellent stability at elevated temperatures, [ 31 ] which can provide extra nucleation sites for the subsequent oxides formation in the initial stage of oxidation. [ 38 ] That is, ZrO 2 particles promote the formation of Mn‐rich oxides (MnCr 2 O 4 , Mn 2 O 3 ) in the outer layer of oxide layer.…”