자료유형  

 학위논문

Control Number  

0017164079

International Standard Book Number  

9798384059455

Dewey Decimal Classification Number  

539.76

Main Entry-Personal Name  

Dabney, Tyler Alexander.

Publication, Distribution, etc. (Imprint  

[S.l.] : The University of Wisconsin - Madison., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

274 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-03, Section: B.

General Note  

Advisor: Sridharan, Kumar.

Dissertation Note  

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2024.

Summary, Etc.  

요약Zirconium alloys (Zr-alloys) have been used as materials for fuel cladding (tubes that contain the uranium-bearing fuel) on account of their high neutron transparency, strength, and corrosion resistance. Several generations of Zr-alloys have been developed with minor adjustments in already low concentration of alloying elements (e.g., Fe, Sn, Nb, Cr) with the goal of imparting improvements to high temperature strength and corrosion resistance. In recent years, there has been a drive to enhance the oxidation resistance and accident tolerance of Zr-alloy fuel cladding in loss-of-coolant accident (LOCA) scenarios, where the temperature can significantly exceed the normal reactor operating temperature. A potential solution is to apply a thin coating of an oxidation-resistant material to the outer surface of the Zr-alloy cladding. This research focuses on the development of chromium (Cr) coatings using cold spray deposition technology. Although not the focus of this study, such a coating can potentially enhance the ballooning and bursting resistance of the cladding, a requirement for the use of economically attractive higher enrichment, higher burnup fuel. In cold spray, powder particles of the coating material are propelled at supersonic velocities towards the surface of a substrate, where upon impact they plastically deform at high strain rates to form a coating. The particle temperature is low, and deposition occurs in solid state. The research was conducted using the commercial 4000-34 CGT cold spray facility at the University of Wisconsin, Madison.This research focused on four areas crucial to the development of Cr cold spray coatings on Zr-alloy for advanced nuclear fuel cladding, namely: (i) coating formation mechanisms, (ii) irradiation effects, (iii) mechanical behavior of the coating and coating-substrate system, and (iv) hydrothermal corrosion and high temperature oxidation of the coatings. The research was conducted using powders referred to in this thesis as electrolytic soft Cr powders, that were produced commercially by a combination of an electrolytic method and a gentle impact milling process. Zr-alloys used in reactors for cladding, namely Zircaloy-4, ZIRLOTM, and Optimized ZIRLOTM (OPZ) in either flat or tubular cladding geometry were used as substrates for various phases of this research. Deposition was conducted using either nitrogen or helium or a mixture of these carrier gases to propel the particles though the converging-diverging de Laval nozzle and to then accelerate them at supersonic velocities towards the substrate.  Given the importance of the powder microstructure in solid state processes such as cold spray, extensive characterization of the feedstock Cr powder particles was conducted using techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscattered diffraction (EBSD), transmission Kikuchi diffraction (TKD), and X-ray diffraction (XRD). The powders were phase-pure and consisted of large grains in the central regions and fine elongated nanocrystalline grains near the edges, a result of the manufacturing route. Nanoindentation tests of the powders showed low hardness - a beneficial feature for cold spray - as it is indicative of the ability of the particles to plastically deform upon impact. Coating depositions were performed by varying select parameters that are known to profoundly influence the microstructure and other characteristics of the coating, including carrier gas composition, gas preheat temperature, and gun traverse speed. Dense thick coatings (25 to over 150 µm) with strong adhesion to the substrate were achieved. Typical of cold spray, the coatings exhibited a heterogeneous structure over multiple length scales, consisting of elongated and dynamically recrystallized grains (ultrafine to nanocrystalline), high dislocation density and strained structures, gradation in grain size, and interparticle boundaries. A fundamental understanding of the coating formation mechanisms both in the interfacial bonding and buildup phases was achieved by single particle impact studies of Cr-on-Zr-alloy and Cr-on Cr, respectively. Cold spray parameters were adjusted to deposit individual Cr particles on these substrates, leading to the identification of two regimes of impact and two distinct sets of critical velocities for bonding. Deposition efficiency was measured by taking the ratio of the number of adhered particles to the total number of particles impacted as a function of particle velocity, and the critical velocity was determined as the velocity where deposition efficiency became non-zero. The particle velocity was predicted using computation fluid dynamics (CFD) codes. For the Cr-on-Zr system, characterization of impacted particle cross-sections using SEM and EBSD revealed that changes due to impact were confined to the outer regions of the Cr particle,while the near-interface regions of the Zr-alloy consisted of a dynamically recrystallized nanograined structure. High resolution TEM (HR-TEM) imaging and Fast Fourier Transform (FFT) analysis showed the evolution of crystallographic coherency between the. (Abstract shortened by ProQuest).

Subject Added Entry-Topical Term  

Nuclear engineering.

Subject Added Entry-Topical Term  

Mechanical engineering.

Subject Added Entry-Topical Term  

Materials science.

Subject Added Entry-Topical Term  

Engineering.

Index Term-Uncontrolled  

Accident tolerant fuel

Index Term-Uncontrolled  

Cold spray

Index Term-Uncontrolled  

Corrosion

Index Term-Uncontrolled  

Cr coated Zr-alloy

Index Term-Uncontrolled  

Irradiation effects

Index Term-Uncontrolled  

Plastic deformation

Added Entry-Corporate Name  

The University of Wisconsin - Madison Materials Science and Engineering

Host Item Entry  

Dissertations Abstracts International. 86-03B.

Electronic Location and Access  

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Control Number  

joongbu:657750