Overview of processing technologies for tungsten-steel composites and FGMs for fusion applications

Tungsten is a prime candidate material for the plasma-facing components in future fusion devices, e.g. ITER and DEMO. Because of the harsh and complex loading conditions and the differences in material properties, joining of the tungsten armor to the underlying construction and/or cooling parts is a complicated issue. To alleviate the thermal stresses at the joint, a sharp interface may be replaced by a gradual one with a smoothly varying composition. In this paper, several techniques for the formation of tungsten-steel composites and graded layers are reviewed. These include plasma spraying, laser cladding, hot pressing and spark plasma sintering. Structure, composition and selected thermal and mechanical properties of representative layers produced by each of these techniques are presented. A summary of advantages and disadvantages of the techniques and an assessment of their suitability for the production of plasma-facing components is provided.