**5. Conclusions**

X-ray microspectral studies established that during vacuum brazing of dissimilar joints, molybdenum-stainless steel using brazing filler metal based on the Cu-Mn-Ni-Fe-1Si system in the central zone of the brazed seam forms a copperbased solid solution structure. The mapping showed that dispersed particles of 0.5–1 μm size, enriched in iron and silicon, precipitate in the copper-based solid solution. The peripheral zone of the seam (on the molybdenum side) is formed by reactive layers, based on iron (width 5.3 μm) and based on molybdenum (width 3.2 μm), which stand out in the form of continuous strips along the soldered seam. At a silicon concentration in the brazing filler metal (1%), these zones are enriched in the latter, which leads to the formation of silicides at the interface and cracking.

It is shown that when using brazing filler metal based on the Cu-Mn-Ni system (Tn = 1100°C), the base metal is dispersed with the release of particles based on iron in a solid solution based on copper and reactive layer about 2.4 μm.

Lowering of brazing temperature to 1084°C allows avoiding base metal dispersion. It ensures the formation of brazed seams with the homogeneous solid solution structure based on copper and single dispersed inclusions of the phase enriched in iron. It was found that the width of the reactive layer decreases to 1.7–1.80 microns, but the concentration ratio of chemical elements remains the same as at a temperature of 1100°C. In some areas, brazing filler metal penetration along the grain boundaries of the base metal of stainless steel is observed.

Mechanical testing of brazed joints of molybdenum-stainless steel proved that brazed joints produced with application of brazing filler metal based on Cu-Mn-Ni system are characterized by maximum values of shear strength. Brazed samples fail both in the seam and in the near-seam zone (strength level of 200–210 MPa) and the base metal (molybdenum) at 300 MPa.

Developed technological process of brazing such dissimilar materials as molybdenum and stainless steel can be applied, when producing individual brazed components of dissimilar materials in the nuclear and aerospace industry and at the development of the fusion reactor.

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**Author details**

Maksymova Svitlana

E.O. Paton Electric Welding Institute of the NAS of Ukraine, Kyiv, Ukraine

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: maksymova@paton.kiev.ua

provided the original work is properly cited.

*Vacuum Brazing of Dissimilar Joints Mo-SS with Cu-Mn-Ni Brazing Filler Metal*

*DOI: http://dx.doi.org/10.5772/intechopen.92983*

*Vacuum Brazing of Dissimilar Joints Mo-SS with Cu-Mn-Ni Brazing Filler Metal DOI: http://dx.doi.org/10.5772/intechopen.92983*
