AlNiCoFeCrTiB_X High-Entropy Coatings Prepared by Electron-Beam Cladding

In this study in order to improve the mechanical properties of coatings on steel substrate, the boron element was added to the initial Al-Ni-Co-Fe-Cr-Ti powder mixture to form in-situ strengthening boride phases. The $\mathrm{AlNiCoFeCrTiB}_{\mathrm{x}}(\mathbf{x}=0,0.25,0.5$, and 1 mol) high-entropy coatings were produced by electron-beam cladding (EBC) on steel substrate and the effect of boron element content on the microstructure and mechanical properties of $\mathrm{AINiCoFeCrTiB}_{\mathrm{x}}$ coatings was studied. When the boron content is $\mathbf{x}=0$ and $\mathbf{x}=0.25 \mathrm{~mol}$, both coatings consist of two solid solutions of bec1 and bec2 structure and different lattice parameters. The addition of boron in amount of 0.5 and 1 mol promotes the in-situ formation of TiB<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and $\mathbf{C r}_{2} \mathbf{B}$ boride phases in bec matrix solid solutions. The Vickers hardness and yield strength of the AlCoNiFeCrTiB ${ }_{0-1}$ coatings increase from 8,8 to 14 GPa and from 2440 to 4040 MPa, respectively, and the strengthening effect reflects a significant positive effect of boron.