Distribution of Alloying Element Atoms between γ- and γ'-Phase Particles in a Heat-Resistant Nickel Alloy

Results of the study of the chemical composition of contacting γ- and γ'-phase particles in a granular heat-resistant nickel alloy (HNA) VV751P (Ni–15Co–12Cr–0.7V–0.3C–0.9W–2.7Mo–3.4Ti–2.0Nb–8.3Al–0.02Hf–0.008B, at %) by atom probe tomography are analyzed. Experimental and literature data on the preferential location of alloying elements in γ- and γ'-phase particles in different heat-resistant nickel alloys are considered. A criterion for the characterization of each of elements based on the ratio K = Е_v/r² (where Е_v is the number of valence electrons and r is the atomic radius of an element) is suggested. It is shown that the higher the K value, the more probable the enrichment of γ-phase particles in this element and the higher the degree of such an enriching. The lower the K value, the more probable the enrichment of γ'‑phase particles in this element and the higher the degree of such an enriching. The effect of γ- and γ'-forming elements in heat-resistant nickel alloys and other factors on the stability of the γ- and γ' phases, mechanical characteristics of disc heat-resistant nickel alloys at room temperature, and long-term strength at operating temperatures is discussed.