Structures, mechanical properties and thermal stability of TiN/SiN x multilayer coatings deposited by magnetron sputtering

Abstract

Polycrystalline TiN/SiN x multilayer coatings with different modulation periods were deposited by reactive magnetron sputtering Ti and Si targets, respectively, and annealed at different temperatures in a vacuum furnace. Their structures and mechanical properties were characterized using X-ray reflectivity, X-ray diffraction and nanoindentation experiments. The results showed that both modulation period and annealing treatment had a significant influence on the structures and mechanical properties for multilayer coatings. As modulation period was below 5.03 nm the preferred orientation for TiN layer in multilayer coatings was (1 1 1), while above 10.05 nm the preferred orientation turned to (2 0 0). The hardness for coatings reached a maximum value of 38.27 ± 0.30 GPa as modulation period was 5.03 nm, but the internal compressive stress decreased with an increase in modulation period. It was found that thermal stability of TiN/SiN x multilayer coatings depended on modulation period, and large modulation period had a relatively high thermal stability. An enhancement in hardness for the as-deposited multilayer coatings, compared to either TiN or SiN x single layer film, could be attributed to the presence of internal compressive stress and the effect of interface strain and quantum trapping in the interfaces. The resistance to plastic deformation for the obtained coatings was reduced after annealing treatment.