Ablation resistance of tungsten carbide cermets under extreme conditions
File(s)
Accepted version
Author(s)
Humphry-Baker, Samuel A
Ramanujam, Prabhu
Smith, George DW
Binner, Jon
Lee, William E
Type
Journal Article
Abstract
A cobalt-free tungsten carbide cermet (WC-FeNi) has been subjected to oxyacetylene flame tests to simulate extreme operating conditions such as a worst-case fusion reactor accident. In such an accident, air-ingress to the reactor may impinge on components operating at surface temperatures in excess of 1000 °C, leading to tungsten oxide formation and its subsequent hazardous volatilisation. Here, the most challenging accident stage has been simulated, where the initial air-ingress could lead to extremely rapid air-flow rates. These conditions were simulated using an oxidising oxyacetylene flame. The separation between flame nozzle and sample was varied to permit peak surface temperatures of ~950–1400 °C. When the peak temperature was below 1300 °C, the cermet gained mass due to the dominance of oxide scale formation. Above 1300 °C, the samples transitioned into a mass loss regime. The mass loss regime was dominated by ablation of the scale rather than its volatilisation, which was confirmed by performing a systematic thermogravimetric kinetic analysis. The result was unexpected as in other candidate shielding materials, e.g. metallic tungsten, volatilisation is considered the primary dispersion mechanism. The unusual behaviour of the cermet scale is explained by its relatively low melting point and by the lower volatility of its FeWO4 scale compared to tungsten's WO3 scale. The substantially lower volatility of the WC cermet scale compared to metallic W indicates it may have a superior accident tolerance.
Date Issued
2020-12-01
Date Acceptance
2020-08-13
Citation
International Journal of Refractory Metals and Hard Materials, 2020, 93
ISSN
0263-4368
Publisher
Elsevier BV
Journal / Book Title
International Journal of Refractory Metals and Hard Materials
Volume
93
Copyright Statement
© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Identifier
https://www.sciencedirect.com/science/article/pii/S0263436820302328?via%3Dihub
Subjects
Materials
0912 Materials Engineering
Publication Status
Published
Article Number
ARTN 105356
Date Publish Online
2020-08-18