Fundamental studies of stress distributions and stress relaxation in oxide scales on high temperature alloys

Technical Report · Tue Jul 02 00:00:00 EDT 1991

OSTI ID:5994751

Shores, D A; Stout, J H; Gerberich, W W

The performance of high temperature alloys in oxidizing environments is crucial to many energy producing and energy conversion technologies. Good high temperature alloys are protected from oxidizing and corrosive environments by the growth of a compact, continuous and protective oxide scale. These scales are subjected to stresses from a variety of sources, including the growth process itself, thermal excursions and in some cases from loads imposed by the application. As a result, the oxide scales may fracture and spall, and the substrate alloy will be quickly re-oxidized: the cyclic repetition of spalling and re-oxidation is a common mode of oxidation degradation at high temperatures. This progress report describes accomplishments during the past year in three areas. First, we have had excellent success in measuring strains in the oxide scale and in the metal substrate at the temperature of oxidation by in situ X-ray diffractometry. In addition, we have carried out a careful theoretical analysis of diffraction from a strain gradient, and as a result we have discovered, in principle, a technique to measure the strain gradient. We have not yet reduced this understanding to practice. Second, we have begun work to develop a statistical characterization (model) of oxide film cracking and spalling, an aspect of the problem that has not previously been explored. Experimentally, this will involve the measurement of cracking events by acoustic emission techniques, and part of that effort will be devoted to an attempt to quantitatively calibrate the acoustic emission data by the use of a micro-indentation technique. Thirdly, we are continuing modeling studies that address the issues of residual stresses and stress relaxation in oxide scale/metal systems. The goal of this work is to develop a fundamental understanding of the origin of strains (and stresses) in oxworking toward the goal of developing a general understanding of the source of strains.

• Research Organization: Minnesota Univ., Minneapolis, MN (United States). Corrosion Research Center
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-88ER45337
• OSTI ID: 5994751
• Report Number(s): DOE/ER/45337-T4; ON: DE92000785
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM OXIDES
OXIDATION
NICKEL OXIDES
CHROMIUM
CRYSTALS
NICKEL
PROGRESS REPORT
PROTECTIVE COATINGS
STRESS RELAXATION
X-RAY DIFFRACTION
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
COATINGS
COHERENT SCATTERING
DIFFRACTION
DOCUMENT TYPES
ELEMENTS
METALS
NICKEL COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RELAXATION
SCATTERING
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
360205* - Ceramics
Cermets
& Refractories- Corrosion & Erosion
360105 - Metals & Alloys- Corrosion & Erosion