Effect of the N2/(Ar+N2) ratio on mechanical properties of high entropy nitride (Cr0.35Al0.25Nb0.12Si0.08V0.20)Nx films

Abstract

The high entropy nitride coatings (Cr0.35Al0.25Nb0.12Si0.08V0.20)Nx with different nitrogen concentrations were fabricated via varying the N2/(Ar + N2) ratio in a RF magnetron reactive sputtering system. The effect of the N2/(Ar + N2) ratio on the crystal structure, chemical composition variation, deposition rate, residual stress, and hardness were investigated in details and revealed in this work. The crystal structure of the metallic coating was amorphous, while the nitride coating exhibited the B1–NaCl structure as the nitrogen concentration of coating exceeded 43 at%. The residual stress was compressive in all coatings, ranging from −0.95 GPa to −3.61 GPa. As the coating nitrogen concentration reached 50 at%, the maximum hardness of this high entropy nitride coating was around 35 GPa and the appealing H/E and H3/E2 value of 0.12 and 0.52, respectively, was also revealed. Finally, a new indicator “composition variation degree” was proposed and employed in this study. This indicator provided a rather effective usage as it could reduce the complexity of defining the composition difference between the deposited coating and the designed value in a multi-component system, especially when the coating nitrogen concentration was varied.