Nano-crystallization of high-entropy amorphous NbTiAlSiW_x N_y films prepared by magnetron sputtering

High-entropy amorphous NbTiAlSiW_x N_y films (x = 0 or 1, i.e., NbTiAlSiN_y and NbTiAlSiWN_y ) were prepared by magnetron sputtering method in the atmosphere of a mixture of N₂ + Ar (N₂ + Ar = 24 standard cubic centimeter per minute (sccm)), where N₂ = 0, 4, and 8 sccm). All the as-deposited films present amorphous structures, which remain stable at 700 ^° C for over 24 h. After heat treatment at 1000 ^° C the films began to crystalize, and while the NbTiAlSiN_y films (N₂ = 4, 8 sccm) exhibit a face-centered cubic (FCC) structure, the NbTiAlSiW metallic films show a body-centered cubic (BCC) structure and then transit into a FCC structure composed of nanoscaled particles with increasing nitrogen flow rate. The hardness and modulus of the as-deposited NbTiAlSiN_y films reach maximum values of 20.5 GPa and 206.8 GPa, respectively. For the as-deposited NbTiAlSiWN_y films, both modulus and hardness increased to maximum values of 13.6 GPa and 154.4 GPa, respectively, and then decrease as the N₂ flow rate is increased. Both films could be potential candidates for protective coatings at high temperature.