Yutao ZHANG is a doctoral student at LaBoMaP and is defending his thesis on "The development of new protective materials for cutting tools during cryogenic machining of alloys for aeronautics."
JURY MEMBERS
Rapporteurs
- Aldo ATTANASIO Professor, University of Brescia
- Nicole FRETY University Professor Charles Gerhardt Montpellier Institute, Balard Chemistry Research Center
Examiners
- Guénael GERMAIN University Professor LAMPA, DIPPE Team (Sustainability, Process Engineering, and Flow Physics), Arts et Métiers Campus Arts et Métiers
- Nicolas MARTIN University Professor FEMTO-ST Institute
- Corinne NOUVEAU Senior Lecturer LaBoMaP, MSE Team (Materials and Surface Engineering), Arts et Métiers Campus Arts et Métiers Cluny
- José OUTEIRO Senior Lecturer LaBoMaP, UGV Team (High-Speed Machining), Arts et Métiers Campus Arts et Métiers Cluny
- Joel RECH University Professor, École Centrale de Lyon - ENISE
SUMMARY
Environmental concerns and the reduction of costs associated with lubricants used in machining have led to increased industrial interest in replacing these liquids with environmentally friendly cryogenic liquids such as liquid nitrogen (LN2). However, research into machining under cryogenic conditions (also known as "cryogenic machining") has shown a wide variation in tool wear and life. This can be explained by the poor performance of the tools currently used at cryogenic temperatures.
The objective of this project is to improve the performance of cutting tools when turning Ti alloys in a cryogenic atmosphere by improving their chemical/mechanical/physical properties. One solution is the application of surface treatments, such as PVD coatings. Many studies have been conducted on the application of coatings to cutting tools in machining, but until now the main objective has been to obtain coatings with thermal stability at high temperatures (over 1000°C). This is typically the case with TiAlN. Our study will therefore consist of optimizing deposits that are thermally stable at very low temperatures (e.g., under liquid nitrogen at -196°C) while withstanding thermal shocks. Indeed, during cryogenic machining, even in an atmosphere at -196°C, the local temperature at the tool/chip contact point can be extremely high.
This study can be divided into the following tasks:
- Optimization of monolayers such as CrN and AlCrN by varying two parameters: deposition temperature and substrate bias voltage.
- Develop multilayers such as Cr/CrN/AlCrN, varying two parameters: the thickness of each monolayer and the number of interfaces or the number of each monolayer.
- Characterize these different coatings (SEM + EDS, XRD, stresses, hardness, adhesion, XPS, thermal properties, etc.) to determine the optimal single and multi-layers to apply to the pawns for friction testing.
- Perform tribological tests on uncoated and coated tungsten carbide pins with Ti6Al4V titanium alloy, using cryogenic assistance (LN2) and emulsion.
- The best coatings will then be applied to tungsten carbide tools to perform wear tests on Ti6Al4V titanium alloy turning with cryogenic (LN2) and emulsion assistance.
The effect of cryogenic assistance will be compared to emulsion, and the feasibility of the PVD coatings developed during the thesis will be determined after all these tests.
KEYWORDS
PVD coatings, Cryogenic machining, Tribology, Wear mechanisms, Modeling and simulation, Aerospace alloys.
