National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russia, Moscow:

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

The article was attended by the staff of the Department №9 “Physical problems of materials science” NRNU MEPhI – Kalin B. A., Suchkov A. N., Fedotov I. V.

Manufacturers of nozzles for liquid rocket engines from heat-resistant austenitic and austenitic-ferritic steels faced the problem of brittle boron nitride formation in the joints. Joints are obtained using hightemperature diffusion brazing in vacuum by filler metal based on Ni – Cr – Fe – Si – B system. This technology is based on the isothermal solidification of the filler metal melt, occurring due to the diffusion of boron into the base material. The developed boron-free nanocrystalline thin film filler metal Ni – 8Si – 5Nb wt.% was proposed to solve the brittle boron nitride problem. The melting interval 1103–1120 ^oC of the filler metal is determined by the method of differential thermal analysis. It’s structural and phase state was revealed by X-ray methods. Technological modes of high-temperature diffusion brazing of austenitic and austenitic-ferritic steels have been developed in the temperature range of 1150–1200 ^oС. The metallographic studies of the brazed joint were carried out. To determine the joint strength characteristics, the microhardness was investigated in the brazed zone and mechanical uniaxial tension tests were carried out according to GOST (Russian State Standard) 28830–90. The best result on the tensile strength 450±30 MPa was achieved on samples obtained at an isothermal holding temperature of 1150 ^oC for 30 min. As a result of this work, the possibility of using boron-free nanocrystalline thin film filler metal for brazing heat-resistant nitrogen-containing steels has been demonstrated. High-strength joints were obtained.

This work was supported by the MEPhI Academic Excellence Project.

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