Effect of deposition parameters on the superhardness and stoichiometry of nanostructured Ti–Hf–Si–N films
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Superhard nanostructured Ti–Hf–Si–N coatings (films) possessing high physical and mechanical properties have been produced. Nuclear and atomic physical analyses, such as RBS, SIMS, GDMS, SEM-EDXS, XRD, and nanoindentation were used to investigate the elemental and phase composition and the morphology of the films as functions of the pressure in the chamber and of the bias voltage applied to the substrate. It was observed that as the grain size in nc-(Ti, Hf)N coatings was decreased from 6.7 to 5 nm and α-Si3N4 (amorphous or quasi-amorphous phase interlayer between nanograins) formed, the coating nanohardness increased from 42.7 to 48.4 ± 1.6 GPa. However, the further decrease of the (Ti, Hf)N grain size to 4.0 nm resulted in a slight decrease in nanohardness. The stoichiometry of the films changes from (Ti40–Hf9–Si7.5)N46 to (Ti28–Hf18–Si9)N45, and also changed the lattice parameter of the (Ti, Hf)N solid solution. It should be noted that the high-hardness coatings showed the least friction coefficient (0.2), and its value remained unchanged until the coating worn out.
Keywordssuperhard nanostructured two-phase coatings Ti–Hf–Si–N elastic modulus friction coefficient elemental composition stoichiometry
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