Evolution of Microstructure and Phase Composition of Single Crystals of Nickel-Based Superalloy in the Process of High-Temperature Creep

A series of long-term strength tests were conducted on [001] single crystals of an experimental nickel-based rhenium-ruthenium superalloy of the sixth generation. The tests were conducted at temperatures of 1100, 1150 and 1200°C for durations of up to ~1100 h. The long-term strength of the alloy at these temperatures is determined by the volume fractions of lamellar particles of γ'-phase and topologically close packed (TCP) phase in the raft structure of the alloy. The mechanism of TCP phase formation in the alloy has been established and identified as δ-phase based on rhenium and ruthenium with a HCP crystal lattice with the parameters а = b = 0.273 nm, c = 0.432 nm and [110]γ || [1 $$\bar {2}$$ 10]δ, and ( $$\bar {1}$$ 1 $$\bar {1}$$ )γ || (0001)δ orientation relationships.