Compositionally Complex Refractory Metal Nitride Coatings: The Effects of V, Nb and Ta on their Structure and Mechanical Properties

The structure evolution and mechanical behavior of the reactive DC magnetron sputtered complex concentrated (or compositionally complex) nitride RM-TiZrHf-N y coatings with variable nitrogen stoichiometry with RM = V, Nb, and Ta were compared with the reference (TiHfZr)-N y coatings over a wide range of nitrogen concentrations. Despite the concentrations of the refractory metals deviated from equimolar concentration, homogeneous solid solutions with cubic structures were present in all coatings. Their mechanical properties depended on nitrogen concentration and RM type. The maximum values of hardness (~43 GPa) and indentation modulus (~530 GPa) were achieved in the reference TiZrHf-N y coatings with (near-) stoichiometric composition. The levels of properties in the coatings with V, Nb, or Ta additions were ~10 % lower and the differences among them were within the scatter of measurements. Thus, the synergy effect from the incorporation of the additional refractory metals into the TiZrHf sub-lattice on mechanical properties was not confirmed.