Nano-hardness, EBSD analysis and mechanical behavior of ultra-fine grain tungsten for fusion applications as plasma facing material

Abstract

Tungsten and its alloys have been extensively studied in order to be used in plasma facing components for future fusion nuclear reactors such as ITER and DEMO. In this work, an evaluation of nano-hardness, microstructure/texture and mechanical behavior using nanoindentation, electron backscatter diffraction (EBSD) and tensile test was performed. The investigated materials were ultra-fine grain lab-scale tungsten and ITER-specification commercial tungsten products, taken as reference in the as-received and annealed (at 1300°C for 1 hour) conditions. Three ultra-fine grain (UFG) tungsten grades were produced under different spark plasma sintering conditions, namely at 2000°C and 70MPa, at 1700°C and 80MPa and, finally, at 1800°C and 80MPa. EBSD analysis provides very relevant data as it is known that the crystallographic orientation affects some features of the surface damage caused by fusion-relevant plasma exposure. The present results will serve as a reference for future studies that will be carried out using plasma-exposed samples in order to correlate the observed damage with the microstructural characteristics and mechanical behavior.

EBSD characterization of pure and K-doped tungsten fibers annealed at different temperatures

“…Figure 8 is an example given for the longitudinal section of the K-doped material. For comparison, random CSL distribution data are plotted in green and labeled as "Random pure W" belonging to a texture-free tungsten produced via spark plasma sintering [46]. Both materials present very similar CSL distributions irrespective of the analyzed section (that is why the authors decided to show only one distribution as an example) with common components at Σ1 (i.e.…”

“…high melting point, high thermal conductivity, high temperature strength and low tritium retention. They became the best candidates to be used as plasma-facing components in future nuclear fusion reactors (ITER) and the demonstration power plant (DEMO) [8,9,[13][14][15][16]. Although tungsten is currently the suitable candidate, some issues still require further investigation and improvement of the material [17,18].…”