The Paton Welding Journal, 2021, №07



2021 №07 (02)

DOI of Article 10.37434/tpwj2021.07.03

2021 №07 (04)

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The Paton Welding Journal, 2021, #7, 13-18 pages

Vacuum brazing of kovar–molybdenum dissimilar joints

S.V. Maksymova, P.V. Kovalchuk and 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

Abstract
The features of spreading of brazing filler metals of Cu‒Mn‒Co system over molybdenum and Kovar were established based on the performed studies. Micro X-ray spectral analysis determined that zonal crystallization of a brazing filler metal drop on the base metal substrate occurs during spreading: pronounced areas of copper-based solid solution (Cu‒12.92Mn‒4.69Co) form along the outer perimeter of the drop, and dendrites of manganese-based solid solution, characterized by a higher melting point, are crystallized in the drop central part. It has been experimentally proven that an increase in the heating temperature contributes to an increase in the spreading area of the brazing filler metal by improving the spreading of copper-based solid solution. It was found that a copper-based solid solution forms in the brazed seam of dissimilar Kovar‒molybdenum joints, and a molybdenum-based reaction layer (about 1 μm wide), crystallizes at the molybdenum-brazing filler metal interface. This layer is enriched in cobalt (15.80 %) and manganese (14.12 %) and contains a small amount of copper (1.63 %). As a result of mechanical tests of Kovar‒molybdenum overlap joints under static loads at room temperature, destruction occurs partly along the brazed seam and partly along the base metal–molybdenum. 14 Ref., 2 Tables, 6 Figures.
Keywords: Kovar, molybdenum, vacuum brazing, dissimilar joints, copper-manganese-cobalt alloys, microstructure, strength, spreading

Received 26.05.2021

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