OJSC Kazan Plant Electropribor, Kazan, Republic of Tatarstan, Russia

М. R. Asadullin, Chief Steel Worker
А. N. Gubaidullin, Engineer of RC

Kazan National Research Technical University named after A.N. Tupolev - KAI, Kazan, Republic of Tatarstan, Russia
S. V. Kuryntsev, Associate Professor, Candidate of Economic Sciences, e-mail: kuryntsev16@mail.ru
R. B. Eksuzyan, Master’s Student

The results of the study of the chemical composition, microstructure, and mechanical properties of nickel-based (chromel, alumel) alloys from different manufacturers are presented. The study of the chemical composition has been conducted using a laser optical spectrometer and a scanning electron microscope (SEM). The study of the macrostructure and microhardness has been conducted on longitudinal and transverse sections of alumel and chromel wires using the Vickers hardness scale, which has been used to calculate the degree of anisotropy for each sample. Thermal EMF measurements and mechanical tensile tests have also been conducted. The results show that some of the samples have a significant degree of anisotropy (HVlng V /HVtrn V = 0.62). The chemical composition of the alumel from one of the manufacturers differs significantly from that of the other two, and the chromel from this manufacturer does not contain cobalt. It has been determined that the presence of cobalt in the alloys can be detected using SEM (up to 1.58%), as the spectral lines of nickel and cobalt overlap when using a spectrometer. The chemical composition of the samples from two manufacturers of chromel has shown that they contain up to 0.8% cobalt. The mechanical properties and thermal EMF of all the studied samples meet the requirements of regulatory documentation. Due to the fact that the state of supply, macro- and microstructure, chemical composition affect the electrophysical properties, it is recommended to use more accurate equipment for determining the thermal EMF in order to improve the quality of input control and determination of the properties of finished products. Comparison of the chemical composition, microhardness and temporary resistance with the thermal EMF has shown that there is no direct relationship between these characteristics.
The work was carried out at the expense of a grant from the Academy of Sciences of the Republic of Tatarstan, provided to young candidates of sciences (postdoctoral fellows) to defend their doctoral dissertation, perform research, as well as labor functions for scientific and educational organizations of the Republic of Tatarstan within the framework of the state program of the Republic of Tatarstan “Scientific and technological development of the Republic of Tatarstan”.

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