Modification of the surface morphology of atmospheric plasma sprayed tungsten coating for X-ray tube application

Subject Areas : journal of New Materials

S. Ajdari ¹ , F. Shahriari Nogorani ²

1 - M. Sc., Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz, Iran.
2 - Assistant Professor, Materials Science and Engineering, Shiraz University of Technology, 71557-13876 Shiraz, Iran

Received: 2017-10-02 Accepted : 2018-01-06 Published : 2018-07-23

Keywords: Atmospheric Plasma Spraying (APS), Chemical Vapor Deposition (CVD), Annealing in hydrogen atmosphere, APS-Wcoating,

Abstract :

    Thick tungsten coatings are used in diagnostic X-ray tube anode applications. Surface roughness has an important role in producing high quality diagnostic images, therefore it is crucial to develop and maintain a smooth anode surface. In order to improve the efficiency of such tubes, surface morphology of the plasma sprayed tungsten coatings was studied in the as-sprayed conditions, hydrogen annealed and top-coated with a chemically vapor deposited tungsten film. Hydrogen annealing was carried out in a wet hydrogen atmosphere at 1500 °C for 90 minutes. Chemical vapor deposition was carried out in a bed of tungsten oxide at 1000 °C. Surface morphology was evaluated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry and stylus-type roughness measurement instrument. The results showed that the suggested post treatments could alter the surface morphology from an oxidized and rough surface to a metallic and smooth morphology. The surface of the final coating was covered by a thin layer of fine tungsten crystals with average roughness of less than 1 micrometer.

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