Microstructure and thermal properties of unalloyed tungsten deposited by Wire + Arc Additive Manufacturing

TL;DR

This study investigates the microstructure and thermal properties of tungsten produced by Wire + Arc Additive Manufacturing, demonstrating its suitability for nuclear applications due to favorable microstructure and thermal characteristics.

Contribution

It provides detailed microstructural and thermal property analysis of additively manufactured tungsten, showing minimal microstructural change after heat treatment and confirming its potential for nuclear sector use.

Findings

Microstructure mainly large elongated grains in as-deposited and heat-treated tungsten

Heat treatment at 1273 K for 6 hours has negligible effect on microstructure and thermal diffusivity

Thermal diffusivity and conductivity decrease with temperature between 300 K and 1300 K

Abstract

Tungsten is considered as one of the most promising materials for nuclear fusion reactor chamber applications. Wire + Arc Additive Manufacturing has already demonstrated the ability to deposit defect-free large-scale tungsten structures, with considerable deposition rates. In this study, the microstructure of the as-deposited and heat-treated material has been characterised; it featured mainly large elongated grains for both conditions. The heat treatment at 1273 K for 6 hours had a negligible effect on microstructure and on thermal diffusivity. Furthermore, the linear coefficient of thermal expansion was in the range of 4.5x10-6 micron m-1 K-1 to 6.8x10-6 micron m-1 K-1; the density of the deposit was as high as 99.4% of the theoretical tungsten density; the thermal diffusivity and the thermal conductivity were measured and calculated, respectively, and seen to decrease considerably in the temperature range between 300 K to 1300 K, for both testing conditions. These results showed that Wire + Arc Additive Manufacturing can be considered as a suitable technology for the production of tungsten components for the nuclear sector.