Behavior of plasma-sprayed tungsten coatings on CFC and graphite under high heat load

Tungsten coatings of 0.5 and 1 mm thickness were successfully deposited by the vacuum plasma spraying technique on carbon/carbon fiber composite (CFC) , CX-2002U, and isotropic fine grained graphite, IG-430U. High heat flux ex periments by irradiation of electron beam with uniform profile were perform ed on the coated samples in order to prove the suitability and load limit o f such coating materials. Heat load properties, gases emission, surface mod ification and structure changes of cross-section of the samples were invest igated, Cracks on the surface and exfoliation between the joint interface o f the samples were not formed below the melting point. These results indica ted that the thermal and adhesion properties between the substrate and coat ings were good under high heat Aux. Microstructure of the joint interface o f the sample was changed in the case of a peak temperature at about 2800 de grees C, Many cracks and traces of melted tungsten flow were observed on th e surface after melting and solidification. Large cavities were also formed inside the resolidified tungsten layer. (C) 1999 Elsevier Science B.V. All rights reserved.