Recent progress in the development and industrialization of superhard and tough nanocomposite coatings, which consist of hard transition metal nitride nanocrystals “glued together” by about 1 monolayer of silicon nitride, is summarized and documented by selected illustrative examples. It is shown that already the presently available superhard nanocomposites applied on machining, stamping and forming tools significantly increase their lifetime and the cutting speed, and consequently also the overall productivity of the machining operations. Further improvement of the presently available and newly developed nanocomposite coatings will push the machining technology towards new horizons. Besides of the superhard nanocomposites, also medium hard, but very tough thick coatings with low internal stress applied to forming tools increase their lifetime by at least one order of magnitude.

Industrial applications of superhard nanocomposite coatings

Various approaches to creating multicomponent nanocomposite coatings of high and superhigh hardness (from ≈30 to 100–120 GPa) are reviewed with particular emphasis placed on mechanisms underlying the increase in hardness in thin (≤10 μm) coatings. The deposition technologies considered include magnetron sputtering, ion beam-assisted and vacuum arc depositions. A classification of hard and superhard coatings with high thermal stability is given. Possible applications of such nanostructured coatings are discussed and prospects for the field are outlined.

https://iopscience.iop.org/article/10.3367/UFNe.0179.200901b.0035/pdf

Structures and properties of hard and superhard nanocomposite coatings

Microstructure and properties of TiAlSiN coatings prepared by hybrid PVD technology

High elastic moduli do not guarantee high hardness because upon finite shear electronic instabilities often occur that result in transformation to softer phases. Therefore, the author concentrates on the extrinsically superhard nanostructured materials, which are the most promising. Decreasing crystallite size results in strengthening and hardening because the grain boundaries impede the plasticity (e.g., Hall–Petch strengthening in case of dislocation activity). However, this hardening is limited to a crystallite size down to 10–15 nm below which softening due to grain boundary shear dominates. This softening can be reduced by forming low energy grain boundaries or a strong interfacial layer. In such a way, much higher hardness enhancement can be achieved. The emphasis will be on the understanding of the mechanisms of the hardness enhancement. A special section deals with examples of the present industrial applications of such coatings on tools for machining in order to illustrate that these materials ar...

Recent search for new superhard materials: Go nano!

Synthesis and characterization of super hard, self-lubricating Ti–Si–C–N nanocomposite coatings

Using high frequency plasma chemical vapor deposition (P CVD) at a total pressure of several mbar with TiCl 4 , BCl 3 , N 2 and H 2 as reactants, superhard nanocomposite nc-TiN/a-BN and nc-TiN/a-BN/a-TiB 2 coatings with hardness of 40–50 GPa were reproducibly deposited and characterized in terms of their phase composition, nanostructure, thermal stability, oxidation resistance and mechanical properties. By analogy with earlier studied systems nc-M n N/a-Si 3 N 4 (M=Ti, W, V) and nc-TiN/a-Si 3 N 4 /a- and nc-TiSi 2 , the maximum hardness of the nc-TiN/a-BN and nc-TiN/a-BN/a-TiB 2 coatings was obtained at the percolation threshold when there is about one monolayer of thin continuous tissue of a-BN between the TiN nanocrystals. It was shown that the thermal stability and oxidation resistance of these coatings is fairly high but lower than that of the nc-TiN/a-Si 3 N 4 and nc-TiN/a-Si 3 N 4 /a-TiSi 2 coatings.

D. Azinovic

Papers

Properties of superhard nc-TiN/a-BN and nc-TiN/a-BN/a-TiB2 nanocomposite coatings prepared by plasma induced chemical vapor deposition