High-throughput screening of MoNbTaW-based Refractory High-Entropy Alloys through Direct Energy Deposition in-situ alloying

Abstract

Refractory High-Entropy Alloys (RHEAs) have been presented as attractive materials for high-temperature applications, such as combustion engines for the aerospace sector, due to the possible service temperature increase, which can result in superior yield of the combustion itself. This work presents the combination of CALPHAD simulations with the in-situ alloying of the MoNbTaW system by Direct Energy Deposition (DED) for a high-throughput screening of RHEAs. CALPHAD simulations show that the addition of V and Ti allows a single-phase BCC structure to be kept. For the DED setup available, MoNbTaW single-track deposits were optimised through Response Surface Methodology. Afterwards, in-situ alloying with V was conducted. Microstructural characterisation was assessed at room temperature through SEM/EDS, and the mechanical characterisation was performed at room temperature (RT), 350 °C and 700 °C, through nanoindentation tests. The microstructural characterisation shows that alloying up to 40 at.% V to the base system allows to keep a single-phase structure; however, some segregations are observed. Mechanical characterisation revealed that V alloying of 22 % promotes a 93 % increase in hardness at RT and a 150 % increase at 700 °C. This study contributes to increasing the practical knowledge of RHEAs, thus accelerating the application of these alloys in aerospace applications.