The formation of precipitate free zones and the growth of grain boundary carbides in the nickel-base superalloy NIMONIC PE16

Journal Article · Wed Jan 01 00:00:00 EST 1997 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(96)00139-5· OSTI ID:445336

Maldonado, R; Nembach, E ^[1]

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1. Univ. Muenster (Germany). Inst. fuer Metallforschung

The formation of precipitate free zones (PFZ) along large and small angle grain boundaries has been investigated for bi- and polycrystals of the nickel-base superalloy NIMONIC PE16. This material is strengthened by coherent precipitates of the {gamma}{prime}-phase. The most important result is that the PFZs are caused by the growth of titanium-rich carbides in the grain boundaries. Since titanium is a constituent of the {gamma}{prime}-precipitates, its depletion along the grain boundaries leads to the dissolution of the {gamma}{prime}-particles and hence to PFZs. The former belief that they are due to chromium-rich grain boundary carbides is disproved. The growth rate of the width W of the PFZs is controlled by the volume diffusion of titanium. Until W reaches its final value W{sub final}, W is proportional to the square root of the aging time. The growth rate of the PFZs yields the volume diffusion coefficient of titanium. The W{sub final} is probably governed by the grain boundaries` limited capacity to accommodate titanium-rich carbides.

• OSTI ID: 445336
• Journal Information: Acta Materialia, Vol. 45, Issue 1; Other Information: PBD: Jan 1997
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
NICKEL BASE ALLOYS
MICROSTRUCTURE
GRAIN BOUNDARIES
PRECIPITATION
CARBIDES
DISSOLUTION
DIFFUSION
AGING
EXPERIMENTAL DATA