EXPERIMENTAL STUDY AND THERMODYNAMIC MODELING OF THE Cr-Fe-Mo-Ti SYSTEM
Résumé
Cobalt constitutes a large part of the radioactive waste in the primary circuit of nuclear reactors. Replacement of cobalt-based hard coatings has been the subject of research for many years in nuclear applications. Up to now, there is no alloy capable to withstand abrasion and corrosion at 350°C and 150 bar pressure during long cycles. Complex concentrated alloys constituted by Cr-Fe-Mo-Ni-Ti have shown promising properties for these applications [1].
The Calphad method was chosen to obtain the most interesting compositions of this system. For this purpose, a critical evaluation of all constitutive subsystems was carried out. Since this system has several Frank-Kasper phases (σ, µ, χ, R, Laves), models were discussed and chosen depending on the crystal structure. Lattice stability and formation enthalpy of stable and metastable compounds were calculated by DFT. It has also been found that some systems lack reliable data or that contradictions are present in the literature. Therefore, experimental determination of phase equilibria in these systems was carried out. Samples of the Cr-Mo-Ti system were synthesized to determine the phase boundaries of the Laves phases and the extension of the Cr-Mo miscibility gap in the ternary system.
[1] G. Huser et al., « Study of the elaboration of high entropy material from powder by laser additive manufacturing », Procedia CIRP, vol. 94, p. 270-275, janv. 2020, doi: 10.1016/j.procir.2020.09.051.