Study On Growth Structure, Superhardness Mechanism And High Temperature Stability Of AlN-Based Nano-Multilayer Films

The application of ceramic thin hard films, such as TiN, on cutting tools remarkably promoted the development of manufacturing industry. With the advancement of high-speed and dry cutting technology, it needs much high requirements for the protection coatings on cutting tools. As the kind of materials that are reinforced by microstructure design, nano-multilayers can not only reach high hardness by the superhardness effect, but also obtain other excellent properties by properly choosing the combination of modulation materials. As a result, nano-multilayers are receiving increasing attentions and researches as a new generation of protection coating.Former researches on superhardness effects and template effects in multilayers are mainly on NaCl structure materials. However, this thesis adopt h.c.p. structured wurtzite AlN(h-AlN) as the crystal layer in the multilayers. The crystallization behavior of SiO₂ and Si₃N₄ under the effects of h-AlN is studied. The superhardness effects as well as the mechanism of hardness enhancement are also investigated. In this thesis, the high temperature oxidation resistance of AlN/SiO₂ are experimental studied. And the effects of SiO₂ addition to the high temperature ability of the multilayers are also discussed.The results are showed as follows. In AlN/SiO₂ and AlN/Si₃N₄ nano-multilayers, due to the h.c.p. AlN template layers, normally amorphous SiO₂ and Si₃N₄ crystallize and form h.c.p. pseudo-crystal structure when their thickness is below 0.6 nm. The crystallized materials grew epitaxially...