Microstructure and phase stability of W-Cr alloy prepared by spark plasma sintering

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.