Initial stages of high-temperature corrosion of Fe-Cr-Ni and Cr-Ni alloys in a carburizing atmosphere of low oxygen partial pressure
The processes of nucleation and growth of metal carbides on the surfaces of Fe-Cr-Ni (25 Cr/20 Ni steel and 25 Cr/33 Ni steel) and Cr-Ni (50/50) alloys in presence of H2/CH4 mixture at 1098 K were investigated. All alloys were studied with surfaces in both cold-worked (CW) and electropolished (EP) conditions. The XPS spectra and the SEM and TEM micrographs revealed formation of transient alpha-Cr2O3 layers on all alloy surfaces during the heat-up period. On the CW surfaces chromium oxide formed homogeneous, compact, fine grained layers whereas on the EP surfaces, the oxide layers developed nonuniformly, with grain and phase boundaries and scratches. Following an incubation period, M7C3 carbides were detected on the surfaces; they grew by replacing the Cr2O3 and through diffusion of metal from the alloy. The mode of nucleation of the M7C3 carbides and their rate of growth depend on the character of the alpha-Cr2O3 transient layers. After removal of Cr2O3 by replacement with M7C3, carbon ingresses into the alloy metal substrate, where M23C6 forms internally. These results are in line with the thermodynamic stability predictions. 29 references.
- Research Organization:
- CEC, Petten, Netherlands; Trinity College, Dublin, Republic of Ireland
- OSTI ID:
- 5701191
- Journal Information:
- Oxid. Met.; (United States), Vol. 24
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHROMIUM ALLOYS
CORROSION
IRON ALLOYS
NICKEL ALLOYS
CHROMIUM OXIDES
COLD WORKING
FOURIER TRANSFORMATION
HEAT RESISTING ALLOYS
INTERMETALLIC COMPOUNDS
MICROSTRUCTURE
NUCLEATION
PHASE DIAGRAMS
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CRYSTAL STRUCTURE
DIAGRAMS
FABRICATION
HEAT RESISTANT MATERIALS
INTEGRAL TRANSFORMATIONS
MATERIALS
MATERIALS WORKING
OXIDES
OXYGEN COMPOUNDS
TRANSFORMATIONS
TRANSITION ELEMENT COMPOUNDS
360105* - Metals & Alloys- Corrosion & Erosion