CALPHAD assessment of the Cr-Fe-Mo-Ti system for the development of high entropy alloys.

International audienceSearching for a suitable replacement for cobalt-based alloyssuch as Stellite 6 [1], whichis used in wear-resistant coatings for nuclear applications, high entropy alloys, or moreaccurately complex concentrated alloys (CCA), have shown some promising properties [2].Alloying elements where chosen considering the chemical composition of the substrate toensure chemical and mechanical compatibility. In our case, this is 316L stainless steel, whichis the most used material in valves and control rods. CCA coatings should provide wear andcorrosion resistance between room temperature and 400°C for long time cycles. Based onthese considerations and previous works [3], we selected the Cr-Fe-Mo-Ti system.Our work aims to develop new alloys using an iterative methodology. It consists increating a robust database using the CALPHAD (Calculation of phase diagrams) method topredict thermodynamic properties. Then we will perform solidification and equilibriumcalculations of different alloys compositions. High-quality database requires reliable data,which will be obtained from the combination of electronic structures calculations by DFT(Density Functional Theory) method with our own experimental work. Using this tool, we willdesign coatings alloys using additive manufacturing techniques according to favourablemicrostructures. Finally, tribology and corrosion tests will be performed on these samples.In this presentation, we will focus on CALPHAD modelling. We will discuss constitutivebinary systems adopted from the literature, and we will assess constitutive ternaries