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Theses

Développement de nouveaux matériaux de protection pour outils de coupe lors d’usinage cryogénique d’alliages pour l’aéronautique

Abstract : Environmental concerns and cost reduction of metal working fluids (MWF) used in machining operations result in ever-growing industrial interest in replacing these fluids with eco-friendly cryogenic fluids such as liquid nitrogen (LN2). However, research on machining under cryogenic conditions (also referred to as “cryogenic machining”) using existing cutting tools (developed for use with common MWF) have shown a large scatter in tool wear, and thus tool life. This scatter can be partially attributed to the subpar performance of the existing cutting tools under cryogenic temperatures. The proposed project aims developing of the next generation of cutting tools for cryogenic machining (milling, turning and drilling). The objective is to enhance the performance of the cutting tools for cryogenic machining by improving the chemical/mechanical/physical properties of the tool materials. One solution to improve the tool life is surface treatments, such as PVD hard coatings. Many studies have been made regarding this topic of research, but so far, the main objective is to obtain coatings that have a high thermal stability at high temperatures (more than 1000°C). This is typically the case of TiAlN. This study is innovative, because it deals with hard protective coatings that will have a high thermal stability at very low temperature (-196°C) but that could also support thermal shocks. Indeed, during cryogenic machining, even under a -196°C atmosphere, the local temperature at tool-chip/work piece contact can be extremely high.This study can be divided into the following tasks:- To optimize monolayers such as: CrN and AlCrN, by varying 2 parameters: deposition temperature and bias voltage on substrate.- To develop multilayers such as Cr/CrN/AlCrN, by varying 2 parameters: thickness of each monolayer and the number of interfaces or number of each monolayer.- To characterize these different coatings (SEM+EDS, XRD, stress, hardness, adhesion, XPS, thermal properties etc) to determine the optimal mono and multilayers to be applied on pins for friction tests.- Tribological tests of uncoated and PVD-coated carbide pins with Ti alloy Ti6Al4V under cryogenic assistance (LN2) and classical emulsion.- The best coatings will then be applied on coated and uncoated tungsten carbide tools for the tool wear tests on turning of Ti alloy Ti6Al4V under cryogenic assistance and emulsion.The effect of the cryogenic assistance will be compared to the emulsion and the feasibility of PVD coatings developed during the thesis will be determined after all these tests.Keywords : PVD coatings, Cryogenic Machining, Tribology, Wear Mechanism, Modeling and simulation, Aeronautic alloys
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Submitted on : Friday, April 8, 2022 - 12:28:16 PM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM
Long-term archiving on: : Saturday, July 9, 2022 - 6:40:07 PM

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  • HAL Id : tel-03635214, version 1

Citation

Yutao Zhang. Développement de nouveaux matériaux de protection pour outils de coupe lors d’usinage cryogénique d’alliages pour l’aéronautique. Mécanique des matériaux [physics.class-ph]. HESAM Université, 2022. Français. ⟨NNT : 2022HESAE009⟩. ⟨tel-03635214⟩

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