Investigation of Tungsten/Steel Brazing Using Nb Interlayer

Abstract:

Due to its excellent thermal physical properties, tungsten is used as structural material in divertor components of fusion reactors. With the rapid development of the technology, the joining of W to reduced activation ferritic/martensitic steel is required for use as a component according to the design of helium cooled high performance divertors. However, W and steel have remarkable differences in their coefficients of thermal expansion, which results in a large residual stress in the joints during the manufacturing and service and consequently leads to failure of the joint. In order to obtain a sound W/steel joint, an appropriate interlayer material inserted between tungsten and steel is necessary to solve the above-mentioned problem. A brazing process, using a Ni–based foil–type filler and a Nb slice as intermediate materials, was carried out in vacuum at 1150 °C for 30 min to investigate the joining of tungsten and steel. The microstructures, chemical composition, hardness and strength of the joint were investigated by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), nanoindentation and tensile strength measurement, respectively. The results show that brazing of W and steel was successfully carried out using a Nb interlayer. The bonding interfaces were bonded well. The average tensile strength of 284 MPa was obtained and all specimens fractured in W near the joining seam, in a brittle fracture mode. The nanoindentation test results indicated that the high hardness of 23 GPa were produced at the W/Ni–based filler brazed seams due to the formation of the Boron–riched phase.

• Periodical: Materials Science Forum (Volume 817)
• Pages: 27-34
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.817.27
• Online since: April 2015
• Authors: Zi Xuan Wang, Yun Zhu Ma*, Wen Sheng Liu, Shu Hua Liu, Qing Shan Cai
• Keywords: Brazing, Interlayer, Steel, Tensile Strength, Tungsten

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