Thickness-dependent hardness of pulsed laser ablation deposited thin films of refractory carbides

Thin films of refractory carbides can find application in energy conversion and tribotechnical devices due to their excellent hardness and high melting temperature. Experiments were performed with pulsed laser ablation deposition of Ti, Zr, and Hf carbide films on silicon substrate. The thickness of the films was varied in the wide range by monitoring the deposition conditions. The hardness of composite film–substrate systems was measured and the intrinsic hardness of the film was separated from the composite system hardness. A model based on an area law-of-mixtures approach was applied taking into account the indentation size effect. The film hardness is revealed to increase with a decrease in thickness, the thickest films being as hard as bulk ceramics. At equal thickness of the films, the hardness decreases with an increase of molar weight of the carbide.