Tuning substrate temperature for improved adhesion and mechanical properties of magnetron sputtered high entropy alloy thin-films

Journal article, 2025

This work reports on the deposition of non-equiatomic CoCrFeNi high entropy alloy (HEA) thin films at various substrate temperatures (Room Temperature (RT), 200 degrees C, 300 degrees C, and 400 degrees C) on EN-24 steel substrates. The deposited films exhibited a preferred {111} crystallographic orientation and possessed a single-phase face centred cubic (FCC) crystal structure. The roughness of the film (R-rms) gradually increased from similar to 1 nm to similar to 4 nm as the particle size grew from similar to 20 nm to similar to 37 nm simultaneously as the substrate temperature increased from 200 degrees C to 400 degrees C, indicating an enhancement in atomic mobility across intergranular interfaces. The hardness of the film reached to a maximum of similar to 17 GPa for the film fabricated at 400 degrees C. This increase is attributed to improved crystallinity, preferential growth orientation and higher columnar density. Notice that this hardness significantly exceeded that of steel substrate, nearly fourfold. The films deposited at 200 degrees C and 300 degrees C exhibited the exceptional adhesion in the incremental load scratch tests, with no signs of delamination. On the other hand, the films deposited at room temperature and 400 degrees C delaminated during the scratch test. The diffusion bond established between the film and the substrate contributed significantly towards the outstanding adhesion of the film, as evidenced by the cross-sectional Transmission Electron Microscopy (TEM) analysis.