Study of cracking and spalling of Cr[sub 2]O[sub 3] scale formed on Ni-30Cr alloy

Journal Article · Wed Dec 01 04:00:00 EST 1993 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00666390· OSTI ID:5156848

Zhang, Y; Shores, D A ^[1]

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1. Univ. of Minnesota, Minneapolis, MN (United States)

Acoustic emission (AE) was used to monitor the scale cracking and spalling of Ni-30Cr alloy samples that had been oxidized at 1000[degree]C for 2 hours or 20 hours then cooled slowly to room temperature in two different ways: natural furnace cooling or constant-rate cooling at a rate of about 19[degree]C/hour. The morphology of the remaining scale and spalled areas was observed by scanning electron microscope (SEM). The AE results show that the scale started to crack and spall continuously during cooling when a certain temperature was reached. The cracking and spalling continued over a temperature range, indicating that there is distribution of the critical-fracture stresses. The SEM analysis shows that the interface between the Cr[sub 2]O[sub 3] scale and the Ni-30Cr alloy substrate is relatively weak. Under this condition, a mathematical model proposed by A. G. Evans can be used to estimate the size of the spalled areas and the critical size of the interfacial flaws required to produce buckling. Measurements of the diameter of spalled areas from SEM images yielded a range of values that were well described by a normal distribution. By applying the Evans model to the AE data, normal distributions of the diameter of spalled areas were estimated, which were 2-3 times larger than the measured sizes. 19 refs., 28 figs., 1 tab.

• DOE Contract Number: FG02-88ER45337
• OSTI ID: 5156848
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 40:5-6; ISSN 0030-770X; ISSN OXMEAF
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ACOUSTIC EMISSION TESTING
ACOUSTIC TESTING
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
CRACKS
ELECTRON MICROSCOPY
MATERIALS TESTING
MATHEMATICAL MODELS
MICROSCOPY
NICKEL ALLOYS
NONDESTRUCTIVE TESTING
OXIDATION
OXIDES
OXYGEN COMPOUNDS
SCALING
SCANNING ELECTRON MICROSCOPY
TESTING
TRANSITION ELEMENT COMPOUNDS