Features of joint structure formation between Kovar and stainless steel using Cu-Mn-Co(Fe) brazing alloy

Abstract The study presents the results of research on the structural formation characteristics of brazed joints between Kovar and corrosion-resistant steel when using brazing alloys of the Cu-Mn-4.5Co-(Fe) system. These characteristics were analyzed depending on the alloy composition and the size of the brazing gap. Metallographic and micro-X-ray spectral studies of dissimilar brazed joints revealed that the use of Cu-Mn-4.5Co and Cu-Mn-Co-2.5Fe alloys results in the formation of joint structures with morphologies that differ significantly from the initial state of the brazing alloys. In both cases, the brazed joints contain a solid solution based on the copper-manganese system. The difference lies in the phases formed: when using the Cu-Mn-4.5Co alloy, a manganese-based phase enriched with iron is formed, whereas the Cu-Mn-Co-2.5Fe alloy leads to the formation of an iron-based phase. It was demonstrated that reducing the brazing gap increases the amount of γ-phase Fex(MnyCozMe), in the joint when using Cu-Mn-4.5Co-2.5Fe, which positively affects the mechanical properties of the joints. This improvement is evidenced by the fracture of samples occurring in the base metal, namely, the corrosion-resistant steel.