Ablation resistance of tungsten carbide cermets under extreme conditions

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Ablation resistance of tungsten carbide cermets under extreme conditions. / Humphry-Baker, Samuel A.; Ramanujam, Prabhu; Smith, George D.W.; Binner, Jon; Lee, William E.

In: International Journal of Refractory Metals and Hard Materials, Vol. 93, 105356, 12.2020.

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@article{1a58cb17860a4cdeb57367515d6d6bce,
title = "Ablation resistance of tungsten carbide cermets under extreme conditions",
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 liquid-phase 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 scales indicates it may have a superior accident tolerance.",
keywords = "Ablation, Neutron shielding, Nuclear fusion, Oxidation, Oxyacetylene flame, Tungsten carbide cermet",
author = "Humphry-Baker, {Samuel A.} and Prabhu Ramanujam and Smith, {George D.W.} and Jon Binner and Lee, {William E.}",
note = "Funding Information: We acknowledge EPSRC support through grant EP/K008749/1 Materials Systems for Extreme Environments. Tokamak Energy Ltd. was an Industrial Partner in this project. We would also like to thank Virtudes Rubio, University of Birmingham, for assisting with oxyacetylene flame tests and Jessica. M. Marshall, Sandvik Hyperion, for providing the WC-FeNi cermet used in this study. Funding Information: We acknowledge EPSRC support through grant EP/K008749/1 Materials Systems for Extreme Environments . Tokamak Energy Ltd. was an Industrial Partner in this project. We would also like to thank Virtudes Rubio, University of Birmingham, for assisting with oxyacetylene flame tests and Jessica. M. Marshall, Sandvik Hyperion, for providing the WC-FeNi cermet used in this study. Publisher Copyright: {\textcopyright} 2020 Elsevier Ltd Copyright: Copyright 2020 Elsevier B.V., All rights reserved.",
year = "2020",
month = dec,
doi = "10.1016/j.ijrmhm.2020.105356",
language = "English",
volume = "93",
journal = "International Journal of Refractory Metals and Hard Materials",
issn = "0958-0611",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - Ablation resistance of tungsten carbide cermets under extreme conditions

AU - Humphry-Baker, Samuel A.

AU - Ramanujam, Prabhu

AU - Smith, George D.W.

AU - Binner, Jon

AU - Lee, William E.

N1 - Funding Information: We acknowledge EPSRC support through grant EP/K008749/1 Materials Systems for Extreme Environments. Tokamak Energy Ltd. was an Industrial Partner in this project. We would also like to thank Virtudes Rubio, University of Birmingham, for assisting with oxyacetylene flame tests and Jessica. M. Marshall, Sandvik Hyperion, for providing the WC-FeNi cermet used in this study. Funding Information: We acknowledge EPSRC support through grant EP/K008749/1 Materials Systems for Extreme Environments . Tokamak Energy Ltd. was an Industrial Partner in this project. We would also like to thank Virtudes Rubio, University of Birmingham, for assisting with oxyacetylene flame tests and Jessica. M. Marshall, Sandvik Hyperion, for providing the WC-FeNi cermet used in this study. Publisher Copyright: © 2020 Elsevier Ltd Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/12

Y1 - 2020/12

N2 - 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 liquid-phase 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 scales indicates it may have a superior accident tolerance.

AB - 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 liquid-phase 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 scales indicates it may have a superior accident tolerance.

KW - Ablation

KW - Neutron shielding

KW - Nuclear fusion

KW - Oxidation

KW - Oxyacetylene flame

KW - Tungsten carbide cermet

UR - http://www.scopus.com/inward/record.url?scp=85090012974&partnerID=8YFLogxK

U2 - 10.1016/j.ijrmhm.2020.105356

DO - 10.1016/j.ijrmhm.2020.105356

M3 - Article

AN - SCOPUS:85090012974

VL - 93

JO - International Journal of Refractory Metals and Hard Materials

JF - International Journal of Refractory Metals and Hard Materials

SN - 0958-0611

M1 - 105356

ER -