Constituting and distribution features of phases in FGH95 nickel base superalloy

Abstract

By means of the electrolytic extraction, microstructure observation and X-ray diffraction analysis, an investigation has been made into the composing and distribution features of the phases in FGH95 nickel base superalloy. The results show that, after solution treated at 1140 °C and aging, microstructure of the alloy consists of γ′, γ phases and the particles of (Nb,Ti)C, (Nb,W)B2, Nb3B2 and Cr23C6 carbide phases, the mass fraction of γ′ and γ phases in the alloy are measured to be 47.8% and 51.2%, respectively, and the mass fraction of carbide phase is about 1%. The fine γ′ phase is dispersedly distributed within the grains, the coarser γ′ phase is distributed in the wider boundary regions. Thereinto, the mass fraction of γ′ phase about 36–60 nm in size is measured to be 30.6%, the mass fraction of γ′ phase about 60–90 nm in size is measured to be 29.1%. The chemical formula of γ′ phase is identified as (Ni0.896Co0.055Cr0.017Fe0.031)3(Ti0.224Nb0.134Al0.473 Mo0.038 W0.066Cr0.064). The parameters of γ′, γ phases are measured to be αγ′ = 0.35986nm and αγ = 0.35912 nm, respectively, and the misfit of γ′, γ phases in the alloy is measured as 0.2058%.