SYMPOSIA PAPER Published: 01 January 1988
STP24547S

Grain Boundary Oxidation and an Analysis of the Effects of Oxidation on Fatigue Crack Nucleation Life

Source

A study on the effects of pre-oxidation on subsequent fatigue life was conducted. The surface oxidation and grain boundary oxidation of a nickel-base superalloy (TAZ-8A) were studied at 600 to 1000°C for 10 to 1000 h in air. The surface oxides were identified and the kinetics of surface oxidation was discussed.

The grain boundary oxide penetration and morphology were studied. The pancake-type grain boundary oxide penetrates deeper and its size is larger, therefore, it is more detrimental to fatigue life than the cone-type grain boundary oxide. The oxide penetration depth, am, is related to oxidation temperature, T, and exposure time, t, by an empirical relation of the Arrhenius type. The effects of T and t on the statistical variation of am were analyzed according to the Weibull distribution function. Once the oxide is cracked, it serves as a fatigue crack nucleus. The statistical variation of the remaining fatigue life, after the formation of an oxide crack of a critical length, could be related directly to the statistical variation of grain boundary oxide penetration depth.

Author Information

Y, Oshida
Syracuse University, Syracuse, NY
HW, Liu
Syracuse University, Syracuse, NY
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Developed by Committee: E08
Pages: 1199–1217
DOI: 10.1520/STP24547S
ISBN-EB: 978-0-8031-5035-5
ISBN-13: 978-0-8031-0944-5