National Research Nuclear University “MEPhI”, Moscow, Russia:

M. A. Penyaz, Post-Graduate Student, Department No. 9 “Physical problems of materials science”, e-mail: mapenyaz@mephi.ru
N. S. Popov, Masters Student, Department No. 9 “Physical problems of materials science”, e-mail: NSPopov@mephi.ru
A. A. Ivannikov, Senior Lecturer, Department No. 9 “Physical problems of materials science”, e-mail: ivannikov7@rambler.ru
O. N. Sevryukov, Associate Professor, Department No. 9 “Physical problems of materials science”, e-mail: sevr54@mail.ru

Cellular structures that are widely used as filters and heat exchangers usually operate under high loads and aggressive environments. Corrosion attack can lead to the destruction of the most vulnerable elements of the structure and, as a result, to the failure of the device. This study is devoted to the influence of the elemental composition of nickel-based brazing alloys on the corrosion resistance of brazed joints. Nickel-based brazing alloys based on Ni – Cr – Si – B (BNi-2, BNi-5a) and Ni – Cr – P (BNi-7) systems, and experimental compositions, were selected for the study. The brazing modes were selected according to differential thermal analysis (DTA). The microstructure of the joints was studied using energy-dispersive Х-ray spectroscopy (EDS) on a scanning electron microscope (SEM). The effect of brazing temperature and holding time on grain size and corrosion resistance were evaluated. Corrosion tests were performed in a boiling mixture of CuSO₄ and H₂SO₄ solutions for 8 hours. The obtained microstructures of the brazed joints with different filler metals and different braze modes, before and after corrosion tests, were compared. The erosion activity of brazing alloys was evaluated, and it was found that an increase in the amount of chromium reduces the damages caused by erosion. The relationships between the chemical composition of the filler metals and the brazed joint, the structural-phase state of the joint and the level of corrosion damage are revealed. The influence of elements such as boron, silicon, molybdenum, phosphorous and chromium on the corrosion resistance of the brazed joint is shown. It was found that BNi-5a, BNi-7 and FM04 show the best corrosion resistance. In brazed joints obtained with low-chromium filler metals, a strong dissolution of the zone adjacent to the base material was detected. The purpose of the study is to determine the influence of elements often used in brazing alloys, as well as the structural-phase state, on the corrosion resistance of the brazed joint.
The reported study was funded by RFBR according to the research project №19-32-90092.

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