Mechanical and tribological properties of Hf1-xMoxNy thin films as a function of Mo contents

Abstract

Ternary transition metal nitrides have procured wide attention towards practical application due to their high hardness, wear resistance and thermal stability. In this study, Hf1-xMoxNy thin films are deposited by reactive direct current magnetron sputtering (R-DCMS) system in an effort to improve further the properties of their analogous binary compounds. In addition, the influence of Mo content on the structure, mechanical and tribological properties of the films are also investigated. The composition and microstructure of the as-deposited Hf1-xMoxNy films are characterized by X-ray diffraction, Raman and scanning electron microscopic techniques. Spectroscopic results show that, as-sputtered Hf1-xMoxNy films mainly consist of single solid solution phase with rock-salt structure. Ultra-micro hardness and ball-on-disc wear tests are conducted to evaluate the mechanical and tribological properties of Hf1-xMoxNy films. The toughness Hf1-xMoxNy films are enhanced, and the film with x = 0.589 shows better mechanical properties, meanwhile, the lowest wear rate of 0.57 × 10−6 mm3/Nm, which is two order magnitudes lower than corresponding binary compounds viz., δ-HfN and γ-Mo2N, and lowest friction coefficient of 0.35 are also obtained. This could be attributed to the effect of solution reinforcement and valence electron concentration. The unique wear resistance of Hf1-xMoxNy is ascribed to the outstanding oxidation resistances and higher H/E and H3/E2 values, which indicate the mechanical properties, wear resistance and anti-friction of δ-HfN and γ-Mo2N can be improved by alloying with each other.