Multi-scale methodology based on experimentation and modeling to design nanostratificated metal / nitride ultra-hard coatings – MULTI-NANO-ULHC

Although nanocrystalline metal nitride coatings are currently used for their outstanding properties such as hardness and wear resistance, improving these properties remains a challenge. Most of them are based on nitrides such as TiN or CrN and their mechanical properties can be improved by combining them with another compound in a ternary nitride system such as (Ti,M)N. Today, the (Ti,Al)N system can be considered as a model system for thin coatings and it will be the starting point of our work. To move towards better performing coatings, one solution consists in depositing TiAl/TiAlN metal/nitride multilayered coatings using a recent sputtering technique (Reactive Gas Pulsing Process RGPP) which allows to easily modulate the stacking of the coating and to take advantage of the properties of the nitride, and the crack resistance of the interfaces.
Recent works carried out by the project team have shown that the period of the stacking, the thicknesses of each component nanolayers and their interfaces strongly impact the hardness particularly when a superlattice effect is evidenced in the TiAl/TiAlN crystallographic structure. In order to save time and raw resources, the actual project aims to establish a MULTI-scale methodology based on experimentation and modeling to allow the rapid design of NANOstratificated Ultra-Hard Coatings for tools or mechanical parts. This methodology, circular and multi-scale, will allow reducing the number of deposited coatings and their characterization and then saving time and raw resources. It is based on the synergy between the expertise of mechanics, chemists and physicists covering the whole chain from the instrument, the acquisition of experimental data, modeling, simulation and updating, until results analysis and exploitation. The method will loop measurement by nanoindentation and associated finite element models (FEM), determination of stable TiAl/TiAlN structures and interfaces using density functional theory (DFT), validation by associated magnetron sputtering deposition of coatings and structural characterization (EDX, XRD, XRR, TEM, HRSTEM, EELS, orientation mapping, etc..). A FEM updating method will allow optimizing the design of the solution coatings. As an indicative output, some tribological behaviors will be check in order to evaluate the possibility to evolve these coatings towards industrial applications. Finally, once the methodology is robust, further development will consist of replacing aluminum (Al) by another M element. Tantalum (Ta), widely used nowadays, will be chosen as an element to confirm that a cubic lattice main growth is preferred in polycrystalline ternary titanium nitride, and favorable to obtain a TiTa/TiTaN multi-nanolayered coating with good mechanical properties. At the end of the project, we expect to have tailored an ultra-hard (Ti,Al)N-based multinanolayered coating with optimized stacking and interfaces and applied this methodology to (Ti,Ta)N-based multilayered thin films. It will radically and for the first time change the design of nanometric multilayered coatings by avoiding to start with many costly and time-consuming deposition campaigns and fine characterizations. For this, the project will start in January 2023 and will last 48 months. It will be developed into three complementary and one indicative workpackages with good risk management and will request two PhD and two MASTER students as additional staff. The MULTI-NANO-ULHC’s leader team will manage the scientific impact, the relations between science and society and socio-economic impacts.