Effect of Electron Beam Remelting Treatments on the Microstructure and Properties of Atmospheric Plasma Sprayed Tungsten Coatings

Atmospheric plasma-sprayed tungsten coating is one of the most prospective plasma-facing materials used in the first wall of nuclear fusion devices since its low tritium inventory, good compatibility, and cost-effective. However, there are still some issues need to be addressed for the atmospheric plasma-sprayed tungsten coatings, such as high porosity and low thermal diffusivity. In this study, electron beam remelting treatments (EBRTs) have been used to modify the surface microstructure of atmospheric plasma-sprayed tungsten coatings, and the properties of the coatings such as porosity, oxygen content, microhardness, wear, and corrosion resistance are characterized and studied systematically. The experimental results revealed that a compact remelted layer with a columnar crystal structure is formed on the surface of the tungsten coating by EBRTs, and the porosity and oxygen content have been significantly reduced. The microhardness of the tungsten coating has nearly doubled after EBRTs. Comparing with the as-sprayed tungsten coating, the wear and corrosion resistance of the electron beam treated tungsten coatings have been considerably improved. Moreover, the thermal diffusivity has also been significantly enhanced.