Manufacturing of W-steel joint using plasma sprayed graded W/steel-interlayer with current assisted diffusion bonding

Ganesh, V. and Dorow-Gerspach, D. and Heuer, S. and Matejicek, J. and Vilemova, M. and Bram, M. and Coenen, J.W. and Wirtz, M. and Pintsuk, G. and Theisen, W. and Linsmeier, C.

Volume: 172 Pages:
DOI: 10.1016/j.fusengdes.2021.112896
Published: 2021

The differences in the thermophysical properties between tungsten and steel create thermal stress peaks at its interface when joined directly for the breeding blanket of a fusion reactor. In order to solve this problem, a graded interlayer made of several layers of W/steel-composites is considered to reduce these stress peaks. Plasma spraying under an argon shrouded chamber was employed as a cost efficient manufacturing technique for such composites and field assisted sintering technology/spark plasma sintering was used to diffusion bond them with bulk-W and bulk-steel. Firstly, thermophysical characterizations were performed on these composites. Secondly, two approaches have been investigated to join bulk-W and 75 vol% W composite: direct joining and using a vanadium foil. Only vanadium foil resulted in successful bond formation at all the three bonding temperatures of 800 °C, 900 °C and 1000 °C. Thirdly, investigation of diffusion bonding parameters (temperature and time) for the joining of 25 vol% W, 50 vol% W, 75 vol% W and bulk-steel were studied and optimum process parameter were identified. Finally, this optimized parameter (1000 °C; 30 min) was employed to manufacture a complete 12 mm x 12 mm W-steel joint consisting of this graded interlayer. © 2021

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