Diffusional transport during the cyclic oxidation of. gamma. +. beta. , Ni-Cr-Al(Y, Zr) alloys

Journal Article · Mon Feb 01 04:00:00 EST 1988 · Oxidation of Metals; (USA)

DOI:https://doi.org/10.1007/BF00656350· OSTI ID:5575730

Nesbitt, J A; Heckel, R W ^[1]

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1. National Aeronautics and Space Administration, Cleveland, OH (USA)

The cyclic oxidation behavior of several cast {gamma} + {beta}, Ni-Cr-Al(Y, Zr) alloys and one LPPS {gamma} + {beta}, Ni-Co-Cr-Al(Y) alloy was examined ({gamma}, fcc; {beta}, NiAl structure). Cyclic oxidation was performed by cycling between 1200{degree}C and approximately 70{degree}C. Oxide morphologies and microstructural changes during cyclic oxidation were noted. Recession of the high-Al {beta} phase was nonparabolic with time. Kirkendall porosity resulting from diffusional transport within the alloy was observed in the near-surface {gamma}-phase layer of one alloy. Concentration profiles for Ni, Cr, and Al were measured in the {gamma}-phase layer after various cyclic oxidation exposures. It was observed that cyclic oxidation results in a decreasing Al concentration at the oxide-metal interface due to a high demand for Al (a high rate of Al consumption) associated with oxide scale cracking and spalling. In addition, diffusion paths plotted on the ternary phase diagram shifted to higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption, and highest Al content, underwent breakway oxidation after 500 1-hr cycles at 1200{degree}C. Breakaway oxidation occurred when the Al concentration at the oxide-metal interface approached zero. The relationship between the Al transport in the alloy and breakaway oxidation is discussed.

• OSTI ID: 5575730
• Journal Information: Oxidation of Metals; (USA), Journal Name: Oxidation of Metals; (USA) Journal Issue: 1-2 Vol. 29:1-2; ISSN 0030-770X; ISSN OXMEA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM
ALUMINIUM ALLOYS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
COATINGS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
DIAGRAMS
DIFFUSION
ELECTRON MICROSCOPY
ELEMENTS
ENGINES
FCC LATTICES
GAS TURBINE ENGINES
HEAT ENGINES
INTERNAL COMBUSTION ENGINES
METALLURGICAL EFFECTS
METALS
MICROSCOPY
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
OXIDATION
PHASE DIAGRAMS
POROSITY
PROTECTIVE COATINGS
SCALING
SCANNING ELECTRON MICROSCOPY
TEMPERATURE EFFECTS
THERMAL CYCLING
TRANSITION ELEMENTS
YTTRIUM
YTTRIUM ADDITIONS
YTTRIUM ALLOYS
ZIRCONIUM
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS