Lanthanum hydride doped tungsten-based coating fabricated by supersonic atmospheric plasma spraying

• LaH2 was added into W and then deposited by supersonic atmospheric plasma spraying.
• La2O3 formed in the LaH2-doped tungsten-based coating by the transformation of LaH2.
• Oxygen content and porosity of the tungsten coating decreased after LaH2 addition.
• LaH2 addition increased the ability of the tungsten coating to resist elastic fracture.
• Fracture toughness of tungsten coating was improved due to introducing LaH2.

In this work, as a kind of rare earth hydrides, 1.5 wt.% LaH2 powder was introduced into a tungsten powder and then deposited by a supersonic atmospheric plasma spraying (SAPS) machine. The purpose was to form La2O3 in the LaH2-doped tungsten-based coating. The microstructure and properties of the undoped and LaH2-doped tungsten-based coatings were characterized using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), nano-indentation tester and Vickers hardness tester. The results showed that SAPS coatings exhibited typical lamellar microstructure. Pores located mainly at lamellar gaps in association with oxidation were also observed. The type of tungsten oxide was mainly WO3. During SAPS process, La2O3 was formed in the LaH2-doped tungsten-based coating by the transformation of LaH2. The formed La2O3 was distributed mainly at lamellar gaps, having a joining effect on the adjacent lamellae. The oxygen content, porosity and thermal conductivity of the LaH2-doped tungsten-based coating were lower than those of the undoped tungsten coating. The introduction of 1.5 wt.% LaH2 in the tungsten coating improved its ability to resist elastic fracture and improved its fracture toughness.