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A Demonstration (DEMO) thermonuclear reactor is the next step after the International Thermonuclear Experimental Reactor (ITER). Designs for a DEMO divertor and the First Wall require the joining of tungsten to steel; this is a difficult task, however, because of the metals’ physical properties and necessary operating conditions. Brazing is a prospective technology that could be used to solve this problem. This work examines a state-of-the-art solution to the problem of joining tungsten to steel by brazing, in order to summarize best practices, identify shortcomings, and clarify mechanical property requirements. Here, we outline the ways in which brazing technology can be developed to join tungsten to steel for use in a DEMO application.

The investigation results of alloys of the Ni-Si-Be system with a various content of Si and Be are presented. Two low-melting eutectics with melting temperatures of the order of 1100 and 915°C have been found out by the methods of differential thermal and X-ray phase analysis and metallography. Two alloys have been selected for the development of brazing filler metals: Ni-5Si-3Be and Ni-6Si-5Be alloys. Three phases have been shown to be components of the binary and ternary eutectics in the Ni-Si-Be system from the side of the nickel angle of the phase diagram. A Ni-5Si-3Be ribbon and fragments of the Ni-6Si-5Be ribbon have been obtained from the selected alloys by rapid quenching. Filler metal of the Ni-5Si-3Be system has been used for brazing samples of the 12Cr21Ni5Ti austenitic-ferritic corrosion-resistant steel at 1150°C for 30 min.

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