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Abstract
Tungsten (W) components with complex shapes will be used in Langmuir probes in ITER and He-cooled divertor in future fusion devices. Metal injection molding (MIM) can be a cost-effective alternative for manufacturing these parts. However, the densification of W during sintering is difficult due to its high melting temperature. A type of in-house developed submicron W and oxide dispersion strengthen W (ODS-W) powder, therefore, has been used for MIM in this study. With the proper powder deagglomeration and binder system, the MIM-W parts for fusion application have been developed. The effects of sintering temperature and hot isostatic pressing (HIP) treatment on MIM-W have been investigated. The resulted MIM W and W-1.2Y2O3 has a relative density higher than 98.2% and 98.6% respectively, and the purity is higher than 99.95 wt.%. The measured thermal conductivity of MIM-W is comparative to that of wrought W at the temperature higher than 500 °C. Thermal shock tests of MIM-W were performed on a 60 kW electron-beam material testing scenario.
Keywords: Metal injection moulding, Tungsten, Ultrafine powder, Fusion devices
1.Introduction
Tungsten (W) has unique properties such as the highest melting point among metals (3422 °C ), high density (19.3 g/cm3), low vapor pressure, chemical inertness, and low erosion rate under plasma condition, which make it one of the most promising candidate materials for the lighting, semiconductor, medical, nuclear power, aerospace, defense industries [1,2]. Due to good thermal physical properties and low retention of tritium compared to graphite or carbon fiber composites (CFC), W has gradually gained prominence as a first wall armor and divertor applications, which is of particular importance for high plasma performance fusion devices [3].
The metal injection moulding (MIM) technology is a feasible and efficient technology for making net-shaped W components in complex geometry with an isotropic homogeneous microstructure, relatively high density, and high purity. Consequently, it is considered a promising production route for development of advanced materials for fusion reactors [4].
In this study, the in-house made ultrafine W and W-1.2 wt.%Y2O3 (W-1.2Y2O3) powder were used to manufacture components by MIM for Langmuir probes in ITER and He-cooled divertor applications. The Langmiur probe, which is fixed with W divertor to detect the plasma status in ITER, include two W parts, the main...