High-entropy alloy inspired development of compositionally complex superhard (Hf,Ta,Ti,V,Zr)-B-N coatings

•Ab-initio calculations show good compatibility of B incorporation in fcc-(Hf,Ta,Ti,V,Zr) N.•Reactive sputtering leads to a mixture of fcc and BN phase with corresponding hardness decrease.•Non-reactive sputtering leads to single-phase fcc coatings with high Zr and C contents and up to 46 GPa hardness.•Vacuum annealing at 1200 °C leads to no phase change in non-reactively sputtered boronnitride coatings.