ALLIHENTROP

Conceptualized in 2004, these alloys with complex compositions contain a large number of metallic elements in equal or close proportions. The random distribution of these elements leads to disordered structures that are translated in scientific language as "high mixing entropy". This atomic-scale disorder gives these materials unique properties that cannot be achieved with conventional alloys. In particular, HEA alloys offer improved hardness and friction resistance, as well as enhanced ductility, i.e. the ability to deform without cracking. They also offer interesting properties in terms of temperature resistance, hydrophobicity and corrosion resistance. However, they cannot be manufactured using conventional methods, as their constituent elements are not evenly distributed during the casting process. Their mechanical properties make them difficult to machine, and complicate their use in the manufacture of solid parts. Their use as coatings on finished parts is therefore the most promising avenue for industrial applications. The cross-border partnership proposed in ALLIHENTROP will pool its skills to propose a new way of synthesizing and processing these special materials in the form of coatings. One of the objectives will be to verify the conversion of their properties at thicknesses of a few hundred nanometers to a few hundred micrometers. The originality of the project lies in the development of simplified deposition methods that are compatible with industrial processes and environmentally friendly. Given the number of possibilities for producing an alloy with 6 different elements in varying proportions, numerical modeling will be carried out to select possible solutions based on their stability. These alloys will then be prepared in powder form by cobrushing (mechanical synthesis). Plasma spraying will be used to deposit thin layers (less than 1 μm). This technique enables very high quality coatings to be obtained in terms of density, and therefore protection against corrosion, uniformity and roughness. Complex synthesis work on 6-element HEA, AlCoCrCuFeNi, in the form of thin films has already been successfully completed. The aim here is to be able to deposit the alloy by plasma spraying from a single solid source (i.e. target) containing all the elements, in order to make the process industrializable. However, this technique has the disadvantage of having to deposit at low pressure (a few milli-tores), which can be problematic for certain SMEs with more limited production tools and investment capacities.