Investigation by fractography of the high-temperature oxidation of the 20%Cr-25%Ni-Nb stainless steel

Journal Article · Fri Apr 01 00:00:00 EST 1988 · Oxid. Met.; (United States)

DOI:https://doi.org/10.1007/BF00751803· OSTI ID:6098562

Desport, J A; Bennett, M J

Simple procedures have been developed for the preparation, by fracture, of transverse corroded metal sections for subsequent examination of the microstructure and microchemistry of the corrosion attack by scanning electron microscopy. Examination of 20%Cr-25%Ni-Nb (20/25/Nb) stainless steel following 120-hr oxidation in carbon dioxide at 1000/degree/C confirmed that the essentially three-dimensional picture revealed by fracture provided additional microstructural information not apparent from optical microscopy of standard metallographically mounted transverse sections. The size and morphology of the oxide grains constituting the various layers of the uniform and the pitting types of external scale were established. Nearest to the underlying steel, a band of the inner Cr/sub 2/O/sub 3/ layer contained a high but variable silicon concentration as well as substantial voidage. Beneath the scale, silica intrusions dramatically influenced the mechanical properties of the 20/25/Nb stainless steel to the depth of this intergranular attack, as fracture at 78 K occurred by a brittle mode. Steel unaffected by oxidation, however, continued to remain ductile.

• Research Organization: Harwell Lab., Didcot, Oxfordshire (England)
• OSTI ID: 6098562
• Journal Information: Oxid. Met.; (United States), Vol. 29:3-4
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON DIOXIDE
CORROSIVE EFFECTS
NICKEL-CHROMIUM STEELS
OXIDATION
NIOBIUM ALLOYS
STAINLESS STEELS
BRITTLENESS
CORROSION
DUCTILE-BRITTLE TRANSITIONS
DUCTILITY
ELECTRON MICROPROBE ANALYSIS
FRACTOGRAPHY
MICROSTRUCTURE
SCALING
SCANNING ELECTRON MICROSCOPY
ALLOYS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
MICROANALYSIS
MICROSCOPY
NICKEL ALLOYS
NICKEL STEELS
OXIDES
OXYGEN COMPOUNDS
STEELS
TENSILE PROPERTIES
360105* - Metals & Alloys- Corrosion & Erosion
360103 - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies