EVIDENCE FOR THE PHENOMENON OF CARBURIZATION-DECARBURIZATION OF TUNGSTEN CARBIDE

Thoriated tungsten filaments acting as the main part of the cathode of magnetrons used for creation of electromagnetic radiation in microwav e ovens were partly carburized in order to limit, during the time of o peration, the volatilization of thorium. The aim of this operation is to create a layer of carbide at the surface of the filament, using a b enzene source. The carburization of tungsten being a reversible chemic al reaction at high temperature, it is quite possible to carry out car burization-decarburization cycles. The interest of this work is to stu dy some parameters leading to the decarburization of partly carburized filaments in order to avoid this phenomenon during fabrication and no rmal use of magnetrons.