Peter Glenn Valentine

US Patent:

6554179, Apr 29, 2003

Filed:

Jul 6, 2001

Appl. No.:

09/900252

Inventors:

Mervyn H. Horner - Del Mar CA
Paul W. Trester - Encinitas CA
Peter G. Valentine - San Diego CA

Assignee:

General Atomics - San Diego CA

International Classification:

B23K 3102

US Classification:

2281221, 228121, 2281241, 2281245, 378143, 378144

Abstract:

Reaction-brazing of tungsten or molybdenum metal bodies to carbonaceous supports enables an x-ray generating anode to be joined to a preferred lightweight substrate. Complementary surfaces are provided on a dense refractory metal body and a graphite or a carbon-carbon composite support. A particulate braze mixture comprising Hf or Zr carbide, Mo or W boride, Hf or Zr powder and Mo or W powder is coated onto the support surface, and hafnium or zirconium foil may be introduced between the braze mixture and the refractory metal body complementary surface. Reaction-brazing is carried out at or near the eutectic point of the components, which may be influenced to some extent by the presence of carbon and boride. Heating to about 1865Â C. for a Mo/Hf combination creates a thin, dense, strong braze that securely joins the two bodies and creates a thin barrier of carbide and boride microphases near and along the interface with the carbon support that diminishes carbon diffusion into the metal body during extended exposures at elevated temperatures (above those presently used in x-ray tubes), even well above the eutectoid temperature.