Si-B Co-Deposition Coatings on an Nb Silicide Based Ultrahigh Temperature Alloy Prepared by Pack Cementation Technique

Abstract:

In order to improve the oxidation resistance of silicide coatings on an Nb silicide based alloy, Si-B co-deposition coatings were prepared at 1150°C for 8 h by using pack mixtures containing different amounts of B powders. The microstructural characteristics of the coatings were studied. The results showed that all coatings had a triple-layer structure. The middle layers of all coatings were composed of (Nb,X)Si₂ (X represents Ti, Cr and Hf elements) and the inner layers of all coatings were composed of (Nb,X)₅Si₃, but the outer layers of the coatings had different phase constituents and morphologies when the amount of B powders in the pack mixture changed. When the amount of B powders in the pack mixture ranged from 0.5 wt% to 12 wt%, the outer layers were composed of (Nb,X)B_2­, with a few CrB₂ particles. When the amount of B powders in the pack mixture was in the range of 0.05~0.1 wt%, the outer layers were composed of (Nb,X)B₂. However, when the amount of B powders in the pack mixture was in the range of 0.02~0.03 wt%, the outer layers were composed of (Nb,X)Si₂, with needle-like (Nb,X)B₂ particles dispersed in it.

• Periodical: Materials Science Forum (Volume 686)
• Pages: 630-636
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.686.630
• Online since: June 2011
• Authors: Yu Zhang, Xi Ping Guo
• Keywords: Nb Silicide Based Alloy, Pack Cementation, Si-B Co-Deposition Coatings

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