Stabilization of complex orthorhombic o-Cr3C2 thin films under high energetic growth conditions: Experiments and calculations

We report on the deposition and characterization of hard and wear resistant orthorhombic Cr3C2 thin films. Films are deposited using a novel linear filtered cathodic arc (LFCA) at high energetic conditions and relatively low substrate temperatures (<200 degrees C). The deposited films have amorphous (a-Cr3C2), nanocrystalline (nc-Cr3C2) and orthorhombic (o-Cr3C2) structure by carefully tuning the growth process via the ion current density and substrate bias voltage. The o-Cr3C2 films presented a moderate stress (-5.3 GPa), low coefficient of friction, low nanowear and high hardness values (33.4 GPa) exceeding in almost 12 GPa the reported hardness values for bulk Cr3C2 (21.5 GPa). Here we show that the generation and relief of compressive stresses in the Cr3C2 films can be controlled through the energy delivered during the growth. The effect of stresses generated by ion bombardment on the mechanical properties of the films was comprehensively studied utilizing ab-initio calculations and compared with experimental results. The hardness increment with compressive stress cannot be assigned only to changes in the electronic structure, but also due to specific microstructural features and chemical bonding of the films. The possibility to deposit the o-Cr3C2 protective films at relatively low temperature on temperature-sensitive substrates shows its potential for industrial applications. (C) 2020 Elsevier B.V. All rights reserved.