Oxide Particle Refinement in 4.5 mass%Al Ni-Based ODS Superalloys

Abstract

Oxide particle refinement, which improves high temperature strength in Ni-based oxide dispersion strengthened (ODS) superalloys, was investigated by employing Hf addition during mechanical alloyed (MA) process. TEM micrographs show that 2 mass% Hf addition makes the smallest oxide particles and shortest separation in the base alloy (Ni–4.5 mass%Al–1 mass% Y₂O₃). Formation of Y₂Hf₂O₇ is confirmed to be responsible for the oxide particle refinement with XRD analysis. By the calculation and comparison based on hardness and Orowan mechanism, the improvement of hardness by Hf addition attributes to the dispersion strengthening of oxide particles.