Yttria-coated tungsten fibers for use in tungsten fiber-reinforced composites: A comparative study on pvd vs. cvd routes

Tungsten fiber-reinforced tungsten (W_f/W) composites are being developed to improve the intrinsic brittleness of tungsten. In these composites, engineered fiber/matrix interfaces are crucial in order to realize toughening mechanisms. For such a purpose, yttria (Y₂O₃ ), being one of the suitable interface materials, could be realized through different coating techniques. In this study, the deposition of thin films of yttria on a 150 µm tungsten wire by physical and chemical vapor deposition (PVD and CVD) techniques is comparatively investigated. Although fabrication of yttria is feasible through both CVD and PVD routes, certain coating conditions such as temperature, growth rate, oxidation of W_f, etc., decide the qualitative nature of a coating to a particular extent. In the case of PVD, the oxidation of W_f is highly reduced compared to the WO₃ formation in high-temperature CVD coating processes. Yttria-coated tungsten fibers are examined comprehensively to characterize their microstructure, phase, and chemical composition using SEM, XRD, and Raman spectroscopy techniques, respectively.