Interface reactions and control of diffusion at the interface between SiC fibres and layer of deposited Fe-9Cr base alloy

The ferromagnetic 9Cr steel EUROFER 97 is considered as a structural material for the first wall of future fusion reactors. To solve a problem of limitation of the maximum operation temperature of 550 °C for EUROFER 97, a new metal matrix composite SiC/EUROFER 97 is proposed. To create a thermally stable interface between the SiC fibres and the steel matrix, the following interlayers were tested as a diffusion barrier: Cr, Re, W and Re/W. Samples with these interlayers were investigated before and after annealing at 750 °C which is supposed to be the operation temperature of the composite material. To simplify examination of the coatings using available analysis methods (SEM, IBA and XRD), the fibre/steel system was approximated by planar samples with identical layer structure. The experiments with both SiC fibres and planar substrates revealed W to be an efficient diffusion barrier.