Preprint Article Version 1 This version is not peer-reviewed

Microstructure and Composition Evolution of a Fused Slurry Silicide Coating on MoNbTaTiW Refractory High-entropy Alloy in High-temperature Oxidation Environment

Version 1 : Received: 6 July 2020 / Approved: 7 July 2020 / Online: 7 July 2020 (09:43:24 CEST)

How to cite: Han, J.; Su, B.; Meng, J.; Zhang, A.; Wu, Y. Microstructure and Composition Evolution of a Fused Slurry Silicide Coating on MoNbTaTiW Refractory High-entropy Alloy in High-temperature Oxidation Environment. Preprints 2020, 2020070120 (doi: 10.20944/preprints202007.0120.v1). Han, J.; Su, B.; Meng, J.; Zhang, A.; Wu, Y. Microstructure and Composition Evolution of a Fused Slurry Silicide Coating on MoNbTaTiW Refractory High-entropy Alloy in High-temperature Oxidation Environment. Preprints 2020, 2020070120 (doi: 10.20944/preprints202007.0120.v1).

Abstract

The poor oxidation resistance of refractory high-entropy alloys (RHEAs) is a major obstacle for their use in high-temperature engineering applications. Anti-oxidation coating technology is an effective method for improving the oxidation resistance. In this paper, the Si-20Cr-20Fe coating was prepared on MoNbTaTiW RHEA by a fused slurry method. The microstructural evolution and compositions of the silicide coating under high-temperature oxidation environment were studied. The results show that the silicide coating could effectively prevent the oxidation of the MoNbTaTiW RHEA. The initial silicide coating had a double-layer structure; a high silicon-content layer mainly composed of MSi2 as the outer layer and a low silicon-content layer mainly contained M5Si3 as the inner layer. Under high-temperature oxidation conditions, the silicon element diffused from the silicide coating to the RHEA substrate while the oxidation of the coating occurred. After oxidation, the coating was composed of an outer oxide layer and an inner silicide layer. The silicide layer moved toward the inside of the substrate, led to the increase of its thickness. Compared with the initial silicified layer, its structure did not change significantly. The structure and compositions of the oxide layer on the outer surface strongly depended on the oxidation temperature. This paper provides a strategy for protecting RHEAs from oxidation at high-temperature environments.

Subject Areas

refractory high-entropy alloys; fused slurry method; silicide coating; Si-20Cr-20Fe; high-temperature oxidation

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