New WC-Cu composites for the divertor in fusion reactors

Abstract

a b s t r a c tThe requirements for the divertor components of future fusion reactors are challenging and therefore a stimulus for the development of new materials. In this paper, WC-Cu composites are studied for use as thermal barrier between the plasma facing tungsten tiles and the copper-based heat sink of the divertor. Composite materials with 50% vol. WC were prepared by hot pressing and characterized in terms of microstructure, density, expansion coefficient, elastic modulus, Young's modulus and thermal diffusivity. The produced materials consisted of WC particles homogeneously dispersed in a Cu matrix with densifications between 88% and 98%. The sample with WC particles coated with Cu evidenced the highest densification. The thermal diffusivity was significantly lower than that of pure copper or tungsten. The sample with higher densification exhibits a low value of Young's modulus (however, it is higher compared to pure copper), and an average linear thermal expansion coefficient of 13.6 Â 10 À6 C -1 in a temperature range between 100 C and 550 C. To estimate the behaviour of this composite in actual conditions, a monoblock of the divertor in extreme conditions was modelled. The results predict that while the use of WC-Cu interlayer leads to an increase of 190 C on the temperature of the upper part of the monoblock when compared to a pure Cu interlayer, the composite will improve and reduce significantly the cold-state stress between this interlayer and the tungsten.

Synthesis of Tungsten Carbides in a Copper Matrix by Spark Plasma Sintering: Microstructure Formation Mechanisms and Properties of the Consolidated Materials

“…Copper-based materials reinforced by WC particles have high hardness, high electrical and thermal conductivity, and high wear resistance. Due to their attractive properties, WC-Cu compositions are promising as electrical contact materials [12,13], electrodes for resistance welding and electrical discharge machining [14,15], and as heat sink materials for fusion applications [16,17]. WC-Cu composites have been manufactured by nonreactive methods, such as infiltration of molten copper into a porous tungsten carbide preform [18,19], sintering of the ex-situ synthesized WC mixed with copper [12,16,20], and stir casting [13].…”

Investigation of the Implementation of Laser Surface Alloying of Cu with Cr–WC

“…In general, a small fraction (0.7% wt.) of Cr dissolves in the Cu matrix to form a solid solution at eutectic temperature [ 11 ], where most of it is undissolved Cr in the Cu–Cr alloy with a high Cr content, which acts as the second phase.…”

“…Tungsten carbide combines advantageous properties, such as high melting point, good wettability by molten copper and, compared to tungsten, has a higher coefficient of thermal expansion (CTE) and lower thermal conductivity, making it a better choice as a reinforcing phase. Both carbon and tungsten have a very low solubility in liquid copper [ 11 ]. WC is widely used as a hard phase, which has been continuously and extensively researched for years [ 12 ].…”

Comparison of the effects of microwave and spark plasma sintering on the electrical, thermal, and mechanical properties of Cu-LaB6 nanocomposites

“…Cu matrix composites have been developed by reinforcing Cu with various reinforcement particles such as TiB 2 (Ren et al, 2019), TiC (Afzal and Harish, 2020), WC (Dias et al, 2019), ZrO2 (Fathy et al, 2019), SiC (Somani et al, 2018), Al2O3 (Strojny-Nędza et al, 2018), and NbC (Bian et al, 2021). The electrical, thermal, and mechanical properties of Cu matrix composites vary depending on factors such as reinforcement particles and production processes.…”