Авіаційно-космічна техніка та технологія (Aug 2022)
Study of phase formation after diffusion welding in vacuum of nickel-niobium compound
Abstract
Diffusion welding is the ideal solution for joining dissimilar materials. This method is particularly effective if you should get a strong monolithic joint without the formation of a rough weld or solder seam. It is used if it is impossible to use standard fasteners. The main scope of this type of welding is the area of high technologies - aviation, space and other types of heavy engineering. All the advantages make the process indispensable under certain conditions and classify it as a high-tech type. This paper considers compounds of dissimilar metals nickel-niobium. In connection with the formation of many intermetallic compounds between these metals, the technology of diffusion welding in a vacuum was chosen. This method allows you to connect materials without melting due to the mutual diffusion of the components. The welding parameters affect the phase formation of the diffusion zone. To study the phase composition, a method of microstructural, X-ray microanalysis, as well as a state diagram of nickel-niobium, is proposed. When studying the weldability of the nickel-niobium system, samples were made in the form of a cube with a side of 10 mm, which was clamped in a mandrel and filled with Wood's alloy. The samples were not subjected to digestion, since during the polishing process, due to the different hardness of the phases, the structure turned out to be thermal polishing. The proposed scheme made it possible to study in detail the phase composition of individual layers of the diffusion zone, their dimensions and dependence on welding parameters. According to the results of quantitative X-ray microanalysis, we did not obtain accurate data on the phase composition and extent of diffuse layers. Qualitative X-ray spectral microanalysis, which was carried out by continuous scanning with an electron probe through the diffuse zone, made it possible to fix the phase reflections on the concentration curves and to determine the extent of the diffusion layers. For a more visual representation of the arrangement of the phases, a combined nickel-niobium diagram with a concentration curve is considered. The studies carried out made it possible to obtain a high-quality joint with mechanical properties that ensure reliability under operating conditions.
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