Production of tungsten-fibre reinforced tungsten composites by a novel continuous chemical vapour deposition process

Abstract

The brittleness below the ductile-to-brittle transition temperature and the embrittlement during operation are the main drawbacks for the use of pure tungsten in plasma facing components of fusion reactors. Tungsten fibre-reinforced tungsten composites overcome this problem by utilizing extrinsic mechanisms to improve the toughness. Dense samples (>99%) have been successfully produced by a step-wise chemical deposition process of single layers of equally spaced fibres. The sequential deposition process with intermediate vents for the fibre placement leads, however, to inhomogeneities and internal interfaces in the deposited tungsten matrix. A new set-up utilizing a continuous deposition process was developed and used for the fabrication of first samples. These samples were examined by microstructural analysis and compared to material produced by the standard technique. It is shown that this advanced set-up in combination with tungsten fabrics allows the productions of tungsten-fibre reinforced tungsten composite in a more controlled and considerably faster way.