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 (M. Sc., Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz, Iran.)
F. Shahriari Nogorani 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.

References:

References:
1- M.R. Eggleston, M.R. Jackson, M.G. Benz, and G. Reznikov, "Joining ductile refractory metal inserts in X-ray tube Targets", JOM, Vol. 48, 59-64, 1996.         

2- J.B. Lambert and J.J. Rausch, ASM Handbook, Properties and Selection: Nonferrous Alloys and Special Purpose Materials, pp. 1-6, ASM International, Vol. 2, 1990.          

3- E. Lassner, W.D. Schubert, Tungsten properties, chemistry, technology of the element, alloys, and chemical compounds, pp. 283-297, Kluwer Academic / Plenum Publications,New York,  1998.      

4- J. Mathew, R.M. Mohanty, R. Sundaresan, V. Sivan, K. Balasubramanian, "Vacuum plasma etching of 1 wt% La₂O₃ dispersed tungsten", Fusion Engineering and Design, Vol. 85, pp. 824-827, 2010.      

5- H. Bolt, V. Barabash, W. Krauss, J. Linke, R. Neu, S. Suzuki, N. Yoshida, "Materials for the plasma-facing components of fusion reactors", J. Nucl. Mater., Vol. 329–333, pp. 66–73, 2004.

6- S. Deschka, C. García-Rosales, W. Hohenauer, R. Duwe, E. Gauthier, J. Linke, M. Lochter, W. Malléner, L. Plöchl, P. Rödhammer, A. Salito, "Manufacturing and high heat flux loading of tungsten coatings on fine grain graphite for the ASDEX-upgrade divertor", J.

 

 

Nucl. Mater., Vol.  233-237, pp. 645-649,

1996.

7- K. Nakamura, S. Suzuki, T. Tanabe, M. Dairaku, K. Yokoyama, M. Akiba, "Disruption erosions of various kinds of tungsten", Fusion Eng. Des., Vol. 39-40, pp. 295-301, 1998.         

8- V.A. Pavlovskii, "Tungsten galvanic coatings deposited from salt metals", Protection of metals, Vol. 42, pp. 170-173, 2006.           

9- A.A. Khan, J.C. Labbe, A. Grimaud, and P. Fauchais, "Molybdenum and Tungsten Coatings for X-Ray Targets obtained through the Low-Pressure Plasma Spraying Process", Journal of Thermal Spray Technology, Vol. 6, pp. 228-234, 1997.     

10- Z. Zhou, S. Song, W. Yao, G. Pintsuk, J. Linke, S.Guo, C. Ge, "Fabrication of thick W coatings by atmospheric plasma spraying and their transient high heat loading performance", Fusion Eng. Des., Vol. 85, pp. 1720–1723, 2010.

 

11- Z. Zhou, S. Guo, S. Song, W.Yao, C. Ge, "The evelopment and prospect of fabrication of W based plasma facing component by atmospheric plasma spraying", Fusion Eng. Des., Vol. 86,  pp. 1625–1629, 2011.  

12- D. Apelian, M. Paliwal, R.W. Smith, W.F. Schilling, "Melting and Solidification in Plasma Spray Deposition, Phenomenological Review", Int. Met. Rev., Vol. 28, pp. 271-294, 1983.        

13- H. Jianjun, L.Xinjun, C.Jun, L. Yling, Q. Bing, J. Shishou, W. Xisheng, L. Guangnan, "Vacuum annealing enhances the properties of a tungsten coating deposited on copper by atmospheric plasma spray", J. Nucl. Mater., Vol. 432, pp. 16-19, 2013.    

14- A. Mehranian, M. R. Ay, N. RiyahiAlam, H. Zaidi, "Quantifying the effect of anode surface roughness on diagnostic X-rayspectra using Monte Carlo simulation", Medical Physics, Vol. 37, pp. 742-752, 2010.    

15- M. Erdélyi, M. Lajko, R. Kakonyi, and G. Szabo, "Measurement of the X-ray tube anodes’ surface profile and its effects on the X-ray spectra", Medical Physics, Vol. 36, pp. 587–593, 2009.          

16- S. Lee, M-H. H., J-W. Noh, E-P. Kim, Y-S. Park, United States patent No. 2003/0211238 A1, 2003.