On the Role of Niobium Addition on Volume Fraction of η Phase and Hardness of A286 Iron–Nickel-Based Superalloy

摘要

Abstract The hardness of A286 superalloy highly depends on the chemical composition and morphology of the γ′ (Ni3(Al,Ti)) and η (Ni3Ti) phases. In this study, effect of niobium addition on the precipitation of η and the hardness of A286 superalloy was investigated. η phase precipitation was studied in aging from 650 to 900?°C for 2–30?h. Field emission scanning electron microscope equipped with energy-dispersive spectroscopy and optical microscope was employed to characterize phases. Based on microstructural observation, the addition of niobium increased the volume fraction of γ′ phase from 10.7 to 12% and shifting of the transformation of γ′ to η to higher temperatures led to stabilizing of γ′ phase. According to hardness results in aged condition, the presence of niobium in the composition resulted in higher hardness numbers via strengthening of solid solution and a rise in γ′ volume fraction.Graphic Abstract