Skip to Main content Skip to Navigation
Theses

Impact des carbures sur la variabilité des propriétés en fatigue de superalliages pour disques

Abstract : Nowadays, original engine makers are challenged by the environmental requirements imposing drastic decrease of CO2 and NOx emissions. It leads to the development of γ/γ′ nickel-based superalloys to ensure good tensile and fatigue properties and a good oxidation behavior of turbine discs. AD730TM was elaborated for applications up to 700°C and the crack initiation and propagation mechanisms this alloy need to be investigated. Non-metallic inclusions are brittle elements that are sensitive to oxidation. They can act as stress concentration sites and can lead to crack initiation. Low cycle fatigue tests were performed at 450°C and 700°C to determine the tests conditions promoting a crack initiation from such inclusions. Fractographic analyzes revealed that inclusions lead to the specimen fracture when the environmental effects are limited and at high strain or stress ranges.In order to better understand the parameters promoting inclusions cracking, oxidation and in situ tensile tests in a SEM chamber were performed. They highlighted an important volume expansion and the cracking of niobium oxides. A stress threshold necessary to crack inclusions was also determined. To improve the fatigue tests understanding, crack propagation tests were carried out to estimate the crack initiation time according to the temperature and the stress range applied. This crack initiation time is shorter when the cracks initiate within inclusions.
Document type :
Theses
Complete list of metadata

https://tel.archives-ouvertes.fr/tel-03232119
Contributor : Abes Star :  Contact
Submitted on : Friday, May 21, 2021 - 1:06:14 PM
Last modification on : Saturday, May 22, 2021 - 3:25:35 AM
Long-term archiving on: : Sunday, August 22, 2021 - 6:34:56 PM

File

2020ESMA0020_govaere.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-03232119, version 1

Collections

Citation

Adèle Govaere. Impact des carbures sur la variabilité des propriétés en fatigue de superalliages pour disques. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2020. Français. ⟨NNT : 2020ESMA0020⟩. ⟨tel-03232119⟩

Share

Metrics

Record views

116

Files downloads

126