(AlCrMoTiNi)_1-XN_X high entropy ceramic with high hardness and toughness prepared by co-filtered cathodic vacuum arc deposition

High entropy ceramic (HEC) coatings have become candidates for new protective coating due to their high strength. However, the hardness - toughness balance of the ceramic coatings is still a difficult problem to solve. The strong nitride forming elements Al, Ti, Cr, Mo, and the non-nitride forming element Ni were selected as the components of the (AlCrMoTiNi)_1-XN_X HEC coatings to regulate the hardness and toughness. When x = 0 and 0.29, the composite structure of amorphous and metallic Ni phase is observed in these coatings. When x = 0.37, 0.40, and 0.45, the phase structure changes to the composite structure of nanoscale face-centered cubic (FCC) phase, metallic Ni, and amorphous phase. When x = 0.45, the maximum hardness of the HEC coating is 31.25 GPa, and it also has high toughness with a K_IC value of 3.25 MPa m^1/2. The HEC coating with high hardness and toughness also presents excellent wear resistance and corrosion resistance. Therefore, the (AlCrMoTiNi)_0.55N_0.45 HEC coating has potential as a protective coating applied in various areas.