Abstract
Thick and dense tungsten coatings are used in applications such as diagnostic X-ray tube anodes. The current paper reports on depositing tungsten coating by atmospheric plasma spraying and employing different post-coating treatments to improve the density of the coating. Vacuum annealing at 800 and 910 °C, cold iso-static pressing, and hydrogen annealing at 1500 °C were carried out as the post-treatments. Microstructure of the specimens was characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The results showed that vacuum annealing was successful in removing the exposed tungsten oxides. The subsequent cold iso-static pressing compacted the coating microstructure and decreased the porosities. Hydrogen annealing reduced the surface oxides and altered the splat structure to a grain structure. The resultant microstructures were explained and related to the conditions of the post-treatments.
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