Improvement of the fine structure of nickel-based superalloy for the hot tract of aircraftcengine turbines
DOI:
https://doi.org/10.54858/dndia.2025-21-24Keywords:
nickel-based super alloy, alloying elements, crystal lattice, phase composition, structureAbstract
The article presents a methodological approach to establishing relationships between the chemical and phase composition of the nickel-based heat-resistant alloy VZHL 12, which is used in gas turbine construction. As the main feature of the stability of parts, the relationship between the number of alloying elements and the heat resistance (long-term strength) of the alloy is established. At the same time, the alloying limits for the specified alloying elements are established and changes in the composition of the strengthening phase are shown. Mathematical models describing the above-mentioned processes are also proposed.
Establishing dependencies will allow with high accuracy: to predict the phase composition and properties of an alloy of a given class, to modernize existing compositions, and will also allow developing new alloy compositions with the lowest costs.
During the study, it was found that with an increase in the titanium concentration, the amount of the g¢ phase and the temperature of its complete dissolution increase. However, at a content of 6.4 % Ti, a TSP phase (s- phase) is formed in the system, which has the form of plates and significantly reduces the properties of the alloy. An increase in the amount of titanium in the alloy leads to a decrease in the concentration of aluminum, tungsten, molybdenum and niobium in the g¢-phase. The effect of temperature on the lattice parameters of the γ and γ′-phases is shown: the lattice parameters of both phases increase with temperature due to thermal expansion and enhancement of atomic vibrations; the minimum discrepancy is observed at a temperature of 700…800 °C, which corresponds to the optimal values of strength, ductility and creep resistance.
Based on the results of the study, new regression models were created that allow adequate prediction of the chemical composition of the phases based on the chemical composition of the alloy. It is shown that the obtained dependencies vary depending on the element content and are closely correlated with the thermodynamic processes occurring in the system, which are accompanied by a change in the phase composition. The reliability of the obtained models is determined by the coefficient of determination, which for all dependencies was greater than 0.9.
An industrial alloy composition was chosen as an example and a comparison of calculated and practical data was carried out. Based on the results, a recommendation was made for the implementation of the obtained dependencies in industry
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