2022 №05 (05) DOI of Article
2022 №05 (07)

Automatic Welding 2022 #05
Avtomaticheskaya Svarka (Automatic Welding), #5, 2022, pp. 40-46

Features of the structure of molybdenum-covar brazed joints

S.V. Maksymova, P.V. Kovalchuk, V.V. Voronov

E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua

The work presents the results of metallographic and X-ray microspectral studies of molybdenum-Kovar overlap joints, which were produced by vacuum brazing with application of brazing fi ller metal based on Cu-Mn-Co system. The infl uence of soaking at brazing temperature on brazed seam structure formation was studied. Local X-ray microspectral analysis was used to determine the number of structural components of the brazed seam: copper-based solid solution, individual iron-based grains, reaction layer in the form of a continuous band on molybdenum - brazing fi ller metal interface. It was found that longer soaking at the brazing temperature promotes an increase of the reaction layer width from 1 to 3 ~m and leads to formation of a faceted morphology from the brazed seam side and to microcracks initiation in it, but it does not aff ect molybdenum concentration, which at diff erent soaking (1…15 min.) is in the range of 55.81…59.05 wt. %. In the solid solution (matrix) manganese concentration decreases with longer soaking, copper concentration rises, but the quantity of iron practically does not change, and it is in the range of 4.52… 4.95 wt. %. In single grains of the dark phase, observed near the interface with Kovar, longer soaking promotes an increase of iron and nickel concentration and lowering of manganese and copper content. 14 Ref., 3 Tabl., 9 Fig.
Keywords: Kovar, molybdenum, vacuum brazing, brazing fi ller metal, structure, brazed seam, soaking, reaction layer, X-ray microspectral analysis

Received: 07.04.2022


1. Zelikman, A.N. (1970) Molybdenum. Moscow, Metallurgiya [in Russian].
2. Kumar, S., Upadhyay, A., Dinesh Kumar, P., Agarwal, A. (2015) Vacuum brazing of molybdenum-kovar and evaluation of its joint strength. Mat. Sci. Forum, 830-831, 282-285. https://doi.org/10.4028/www.scientific.net/MSF.830-831.282
3. Chen, G., Yin, Q., Guo C. et al. (2019) Beam defl ection effects on the microstructure and defect creation on electron beam welding of molybdenum to Kovar. J. of Materials Proc. Technology, 267, 280-288. https://doi.org/10.1016/j.jmatprotec.2018.12.017
4. Kazakov, N.F. (1986) Diff usion welding of materials. Moscow, Mashinostroenie [in Russian].
5. Guoqing, C., Qianxing, Y., Zhibo, D. et al. (2021) Microstructure evolution analysis for the reaction interface between molybdenum and Kovar acquired by electron beam welding-brazing. Materials Characterization, 171, 110781. https://doi.org/10.1016/j.matchar.2020.110781
6. Petrunin, I.E. (2003) Handbook on brazing. 3rd Ed. Moscow, Mashinostroenie [in Russian].
7. (2006) Mechanical engineering. Encyclopedy: Technology of welding, brazing and cutting. Vol. 111-4. Ed. by B.E. Paton. Moscow, Mashinostroenie [in Russian].
8. Yermolayev, G.V., Kvasnitskyi, V.V., Kvasnytskyi V.F. et al. (2015) Soldering of materials: Manual. Mykolaiv, NUK [in Ukrainian].
9. Kostin, A.M., Labartkava, Al.V.,Martynenko, V.A. (2014) Study of processes of interaction of titanium-containing brazing fi ller metals with oxide ceramics and covar. Metallofi z. Noveishie Tekhnol. J., 36(6), 815-827 [in Russian]. https://doi.org/10.15407/mfint.36.06.0815
10. Singh, M., Asthana, R., Sobczak, N. (2020) Active brazing of SiC-base ceramics to high-temperature alloys. J. of Mater. Eng. and Perform. 29, 4898-4912. https://doi.org/10.1007/s11665-020-04934-3
11. Lyakishev, N.P. (1997) State diagrams of binary metallic systems: Handbook. In: 3 Vol. Vol. 2, Moscow, Mashinostroenie [in Russian].
12. Maksymova, S.V., Voronov, V.V., Kovalchuk, P.V.,. Larionov, A.V. (2017) Producing dissimilar joints of molybdenum- stainless steel using vacuum brazing. The Paton Welding J., 2, 13-18. https://doi.org/10.15407/tpwj2017.02.03
13. Maksymova, S.V., Kovalchuk, P.V., Voronov, V.V. (2021) Vacuum brazing of Kovar-molybdenum dissimilar joints. The Paton Welding J., 7, 13-18. https://doi.org/10.37434/tpwj2021.07.03
14. Maksymova S.V., Voronov V.V., Kovalchuk P.V., Larionov A.V. (2017) Infl uence of temperature of the brazing on structure of brazed heterogeneous molybdenum-stainless steel joints. Metallofi z. Noveishie Tekhnol. J., 39(9), 1227-1237. https://doi.org/10.15407/mfint.39.09.1227

Advertising in this issue: