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Tungsten alloys currently represent prospective candidates to replace tungsten in the first wall applications in future fusion facilities. Tungsten has many advantageous features; however, it is rather susceptible to oxidation at temperatures above around 500 °C. To mitigate/suppress this, various oxide-forming elements are being added to tungsten to induce self-passivation. The most common ones are chromium, titanium and silicon. The alloyed powder is frequently prepared by mechanical alloying and then consolidated by a sintering method. Most of the published results are related to alloys consolidated by HIP process that leads to formation of multiphase material. In the presented study, W-10Cr alloy with hafnium oxide particle dispersion was prepared by spark plasma sintering. Unique features of the microstructure are discussed and compared with other processing methods Phase and thermal stability of the alloy was evaluated at three fusion-relevant temperatures using detailed X-ray diffraction analysis, differential thermal analysis and microstructural observations in a scanning electron microscope. Impact of the heat treatment on crucial properties such as thermal conductivity and heat capacity was evaluated.

In a fusion reactor, the transport of hydrogen isotopes (primarily tritium) has to be controlled, from the point of view of fuel balance and retention in the reactor components, which can result in material degradation and spreading of radioactivity. To suppress this, tritium permeation barriers are developed. Suitable materials for the permeation barriers are those with low hydrogen isotope permeability - primarily ceramic materials, such as oxides, carbides and nitrides. In this study, coatings of six less common nitrides prepared by physical vapor deposition – namely AlCrN, CrN, Cr2N, CrWN, WN and ZrN – were investigated. Besides basic characterization (elemental and phase composition, surface morphology and coating thickness), hydrogen permeation, adhesion, residual stress and thermal expansion were evaluated. All coatings were dense, crack-free and well adherent. The permeation reduction factor which was determined at 400 °C and 1 bar ranged from ˜102 to ˜5 × 103, the best performance being achieved by the ZrN coating. As these materials seem not to be investigated as hydrogen permeation barriers, they have a very high potential to be further improved.