Influence of system alloying and dimensional mismatch of crystalline lattices of g- and g'- phases on the characteristics of the strength of single-crystal nickel superalloys

Abstract

Purpose of the work. Obtaining predictive regression models, by means of which, it is possible to adequately calculate the mechanical properties of monocrystalline nickel-base superalloys without conducting previous experiments. Methods of research. For experimental and theoretical studies of temperature performance, a working sample of alloys is formed consisting of known industrialt nickel-base superalloys for monocrystalline castings of domestic and foreign production, which due to contents of the main elements, cover a wide range of alloying. The obtained values were processed in the Microsoft Office with the least squares method, with the obtaining of the "parameter-property" correlation dependencies with the obtaining of mathematical equations of regression models (trend lines) that describe these dependencies optimally. Received results. The influence of alloying elements on their tendency to the formation of phases in foundry heat-resistant nickel alloys is considered. Based on the influence of elements on phase formation, the coefficient of the ratio of alloying elements Kg¢ in the alloys of this class was first developed. A close correlation dependence of the ratio Kg¢ with a dimensional discrepancy between the γ- and γ-phases crystalline lattice (localized) was found. It has also been shown that for multi-component nickel systems it is possible to predict with high probability misfit, which significantly affects the strength characteristics of alloys of this class. The regression models of correlation dependencies on dimensional inconsistency (γ / γ'-misfit) are given, which allow to predict the boundaries of short-term and long-term strength of alloys. It is shown that the magnitude of the misfit at the operating temperature should tend to zero. This will increase the structural stability by minimizing structural stresses, which has a positive effect on the strength and plastic characteristics. Scientific novelty. For the first time, a coefficient of the ratio of alloying elements Kg¢, which has a close correlation with the strength and dimensional discrepancy of casting nickel-base superalloys, is proposed. Practical value. The perspective and effective direction in solving the problem of forecasting of the main characteristics affecting the complex of service properties of alloys, both in the development of new monocrystalline nickel-base superalloys, and in the improvement of the composition of known industrial brands of this class, is shown.