The Effect of Tungsten Addition on Steam Oxidation Behavior of the Fe-20Cr-35Ni (at%) Alloy at 1073 K

Abstract

This paper focuses on the effect of tungsten addition on the steam oxidation behavior of the Fe-20Cr-35Ni (at%) alloy at 1073 K. Steam oxidation tests of the W added Fe-20Cr-35Ni (at%) alloy were carried out at 1073 K in an Ar-15%H₂O gas mixture for up to 604.8 ks. The oxidation resistance of the alloys was improved by adding W into the alloy. There are two effects of W on the steam oxidation behavior: the effect of solid solution and the effect of precipitation. Tungsten in the alloy is enriched as a Ni-W alloy in the matrix of the internal oxidation zone (IOZ) during oxidation. The Ni-W alloy in the IOZ may act as a diffusion barrier for oxygen and promote a continuous Cr₂O₃ layer. On the other hand, Fe₂W precipitated in the alloy decomposes during oxidation and provides alloying elements for forming FeCr₂O₄ and CrWO₄ in the IOZ, resulting in a continuous Cr₂O₃ layer formation.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 86 (2022) 121–130.

Fig. 11 Cross-sectional BE images of the oxide scale formed on the alloys after the steam oxidation at 1073 K.