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Comportement mécanique à température ambiante d’un revêtement de chrome déposé sur un substrat en alliage de zirconium

Duc Vinh Nguyen 1
1 LC2M - Laboratoire d'Etude du Comportement Mécanique des Matériaux
SRMA - Service des Recherches Métallurgiques Appliquées : DEN/DMN/SRMA
Abstract : The mechanical behavior of a 15 µm-thick chromium coating, deposited on a zirconium alloy substrate by a particular physical vapour deposition process, is studied at Room Temperature (RT) using several experimental techniques at several scales: "biaxial" tests consisting in applying simultaneously an internal pressure and an axial loading on Zr-based alloy tubes coatedwith Cr, in situ tensile tests in SEMon sheet samples coated with Cr. The cracking and plasticity of the coating are studied using two main techniques: acoustic emission and digital image correlation. The results show that, at RT, the first channeling cracks in the coating initiate at 0.3-0.4% macroscopic strain, when the substrate starts to yield. During further loading, the crack density increases first rapidly then more slowly, before reaching saturation. Plastic strain of the non-cracked coating regions is observed, in addition to the increase of crack opening. Until at least 5% applied strain, no interface decohesion of the coating is observed and the cracks, both transgranular and intergranular, do not penetrate significantly into the substrate. Numerical simulations using a FFT-based method (AMITEX_FFTP solver) are performed to calculate the critical energy release rate of the coating. It is shown that the kinetics of the coating cracking is strongly influenced by plastic strain of the substrate. The cracking saturation is due to plastic strain localization in the substrate under the cracks in the coating. The methodology developed here could be applied to study the behavior of the coating when the cladding is irradiated or loaded at higher temperatures, especially at the cladding in-service temperature (~350°C).
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Submitted on : Friday, February 26, 2021 - 11:41:10 AM
Last modification on : Wednesday, April 14, 2021 - 3:38:08 AM

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Duc Vinh Nguyen. Comportement mécanique à température ambiante d’un revêtement de chrome déposé sur un substrat en alliage de zirconium. Mécanique des matériaux [physics.class-ph]. Université Paris-Saclay, 2021. Français. ⟨NNT : 2021UPAST009⟩. ⟨tel-03153296⟩

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