Alloying element diffusion in alloy 800 H (UNS N08810) and alloy 617 (UNS N06617)

Book · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:379689

Maldonado, L; Diaz, L ^[1]; Gruebmaier, H; Naoumidis, A; Nickel, H ^[2]

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1. Unidad Merida (Mexico). Centro de Investigacion y de Estudios Avanzados
2. Research Centre Juelich GmbH (Germany). Inst. for Materials in Energy Systems

Samples of alloy 800 H (LJNS N08810) and alloy 617 (UNS N06617) were oxidized in a simulated process gas atmosphere. The principal elements of the gaseous environment were 50% H{sub 2}O, 35% H{sub 2} and 5% of CO{sub 2}, CO, and CH{sub 4}, respectively. The experiments were carried out at temperatures from 850 C to 950 C for exposures ranging from 600 to 5,000 hours. After the exposure, the alloy surfaces showed compact oxide layers, which resulted in a depleted zone of oxidizing elements in the substrate layer. Using Electron Probe Microanalysis (EPMA), concentration profiles and the extension of the depleted zone were measured. Calculated theoretical profiles were then fitted to the EPMA-measured profiles, using Fick`s second law of diffusion and resolved by a finite difference method and diffusion coefficients as fitting parameters. The diffusion coefficients for chromium may be represented as D = Do exp.(-Q/RT) with the values Do = 11.4 cm{sup 2}/s and Q = 289 kJ/mol for alloy 800 H and Do = 2.1 cm{sup 2}/s and Q = 280 kJ/ mol for alloy 617. The value of the resulting activation energy Q for diffusion in the investigated alloys is similar to that reported in the literature for f.c.c structures.

• OSTI ID: 379689
• Report Number(s): CONF-960389--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOM TRANSPORT
CARBON DIOXIDE
CARBON MONOXIDE
CHROMIUM
CHROMIUM OXIDES
CONTROLLED ATMOSPHERES
CORROSION PRODUCTS
CORROSION PROTECTION
DIFFUSION
EXPERIMENTAL DATA
HYDROGEN
INCOLOY 800H
INCONEL 617
METHANE
MICROANALYSIS
OXIDATION
WATER VAPOR