Abstract
In order to clarify the controversies of hardening mechanism for TiN/SiNx-based nanocomposite films, the microstructure and hardness for TiN/SiNx and TiAlN/SiNx nanocomposite films with different Si content were studied. With the increase of Si content, the crystallization degree for two series of films firstly increases and then decreases. The microstructural observations suggest that when SiNx interfacial phase reaches to a proper thickness, it can be crystallized between adjacent TiN or TiAlN nanocrystallites, which can coordinate misorientations between nanocrystallites and grow coherently with them, resulting in blocking of the dislocation motions and hardening of the film. The microstructure of TiN/SiNx-based nanocomposite film can be characterized as the nanocomposite structure with TiN-based nanocrystallites surrounded by crystallized SiNx interfacial phase, which can be denoted by nc-TiN/c-SiNx model ('c’ before SiNx means crystallized) and well explain the coexistence between nanocomposite structure and columnar growth structure within the TiN/SiNx-based film.
Highlights
As superhard film material, nanocomposite films have been widely investigated in the past decades for use as wear-resistant coatings on tools and mechanical components [1,2]
The nanostructure and hardening mechanism have been widely explained by nc-TiN/a-SiNx model proposed by Veprek et al in 1995 [4], in which equiaxed TiN nanocrystallites were embedded in an amorphous SiNx (a-SiNx) matrix
In summary, in order to clarify the controversies of hardening mechanism for TiN/SiNx-based nanocomposite films, the microstructure and hardness for TiN/SiNx and TiAlN/SiNx nanocomposite films with different Si content were studied
Summary
As superhard (hardness H ≥ 40 GPa) film material, nanocomposite films have been widely investigated in the past decades for use as wear-resistant coatings on tools and mechanical components [1,2]. The nanostructure and hardening mechanism have been widely explained by nc-TiN/a-SiNx model proposed by Veprek et al in 1995 [4], in which equiaxed TiN nanocrystallites (nc-TiN) were embedded in an amorphous SiNx (a-SiNx) matrix. This model is in dispute due to the lack of direct experimental evidence, which mainly reflects in two aspects. Whether TiN crystals are transformed from columnar crystals into equiaxed nanocrystallites is disputed, since there was no direct cross-sectional transmission electron microscopy (TEM) observation for the
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