An Overview of Dispersion-Strengthened Tungsten Alloys as Fusion Plasma-Facing Materials *

Tungsten (W) is a common plasma-facing component (PFC) material in the divertor region of tokamak fusion devices due to its high melting point and high sputter threshold [1,2]. However, W is intrinsically brittle and is further embrittled under neutron irradiation, and the low recrystallization temperature pose complications in fusion environments [1,3].  In the past decade, the Radiation Surface Science and Engineering Lab (RSSEL) has been developing dispersion-strengthened tungsten composite alloys as an alternative PFC W-based material.  These materials have been processed via spark plasma sintering (SPS) with TiC, ZrC, and TaC dispersoids alloyed from 0.5 to 10 weight %. SPS is a powder compaction technique that provides high pressure and heating rates via electrical current, allowing for a lower final temperature and hold time for compaction [4]. Initial testing of material and PMI properties, microstructure, and composition of specimens will be presented. The DS-W materials have shown promise as PFCs indicated by enhanced recrystallization properties at temperatures between 1200-1800 C, oxygen trapping and D and He exhaust management.  However, there remains some outstanding challenges and these will be discussed. High-flux exposures at the Magnum-PSI facility at DIFFER exposed samples to a H fluence of 10²⁶ cm^-2 and He fluence of 10²⁵ cm^-2. In-situ chemistry changes via XPS, ex-situ morphology changes via SEM, and microstructure with TEM will be presented.

 

[1] E. Lassner, W.D. Schubert. Tungsten. 1999. Plenum Publishers.

[2] D. Naujoks, et al. Nucl.  Fusion. Vol 36, No. 6 (1996)

[3] S.J. Zinkle, et al. Annu. Rev. Mater. Res. 2014. 44:241–67.

[4] J.R. Groza, et al. Mat. Sci. and Eng. A287 (2000) 171-177.