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!

Thermal stability of alumina thin films containing γ-Al2O3 phase prepared by reactive magnetron sputtering

Physical vapor deposition technology for coated cutting tools: A review

Compressor blades used in gas turbine engines for marine applications must work in harsh environment such as erosion and corrosion Multilayer nitride coatings produced by physical vapour deposition (PVD) have exhibited promising potential in improving the corrosion resistance In this paper, three types of Ti/TiN multilayer coatings with different thickness ratios (M1: 10 nm/40 nm, M2: 20 nm/80 nm, M3: 30 nm/80 nm) were deposited onto 1Cr11Ni2W2MoV stainless steel substrates by plasma activated electron beam physical vapour deposition (EB-PVD) The microstructure, hardness and corrosion behaviour of the Ti/TiN multilayer coatings and TiN single layer coating were comparatively studied The columnar grain growth of the TiN single layer coating was suppressed by the introduction of the Ti metallic sublayers With the increase of the Ti sublayer thickness, the characteristics of the layered microstructure became more apparent The substrates coated with Ti/TiN multilayer coatings exhibited better corrosion resistance (maximum 87% protection efficiency for M3) and higher hardness value (maximum 341 GPa for M1) than those coated with TiN single layer

Microstructure, hardness and corrosion behaviour of Ti/TiN multilayer coatings produced by plasma activated EB-PVD

Magnetron-sputtered Al2O3 thin films were annealed in ambient air. The phase compositions of the as-deposited Al2O3 films were (i) fully amorphous, (ii) nanocrystalline γ-Al2O3 in an amorphous Al2O3 matrix, and (iii) fully crystalline γ. For all samples, annealing to 1 100–1 150 °C resulted in a transformation to α-alumina. The transformation paths depend on the phase fraction of γ in the as-deposited films. For amorphous films and films with low initial γ fraction, the intermediate phase θ-Al2O3 appeared in the range of 1 000–1 100 °C. For predominantly crystalline γ-Al2O3 as-deposited films no intermediate Al2O3 phases were observed, indicating a direct γ-to-α phase transformation at ∼1 100 °C.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppap.200932301

Thermal Stability and Phase Transformations of γ-/Amorphous-Al2O3 Thin Films

Pulse enhanced electron emission (P3e (TM)) is a new approach in PVD technology for the deposition of metal oxides. The process is dedicated to the formation of alumina-based and other metallic oxide layers and comprises high current pulse technique for the arc sources. The method allows a deposition of hard alumina-based coatings at substrate temperatures below 600 degrees C. Different oxide layers and layer combinations were prepared with this new technique illustrating the enormous potential for the design of wear resistant coatings. The layers were characterized with respect to hardness, stress, composition, crystal structure, and thermal stability. Solid solutions of (Al1-xCrx)(2)O-3 could be synthesized for a composition range of 0.3 <= 5x<l. The growth of the solid solutions has also been demonstrated at TiCN and TiAlN interfaces. (c) 2007 Elsevier B.V. All rights reserved.

Pulse enhanced electron emission (P3e™) arc evaporation and the synthesis of wear resistant Al–Cr–O coatings in corundum structure

A PVD layer system for the coating of workpieces encompasses at least one mixed-crystal layer of a multi-oxide having the following composition: (Me1 1-x Me2 x ) 2 O 3 , where Me1 and Me2 each represent at least one of the elements Al, Cr, Fe, Li, Mg, Mn, Nb, Ti, Sb or V. The elements of Me1 and Me2 differ from one another. The crystal lattice of the mixed-crystal layer in the PVD layer system has a corundum structure which in an x-ray diffractometrically analyzed spectrum of the mixed-crystal layer is characterized by at least three of the lines associated with the corundum structure. Also disclosed is a vacuum coating method for producing a mixed-crystal layer of a multi-oxide, as well as correspondingly coated tools and components.

Layer system with at least one mixed crystal layer of a multi-oxide

A PVD layer system for coating workpieces comprises at least one mixed crystal layer of a polyoxide with the following composition: (Me1 1-xMe2x)2O3. Me1 and Me2 are at least one of the elements Al, Cr, Fe, Li, Mg, Mn, Nb, Ti, Sb or V. The elements of Me1 and Me2 are each different. The crystal lattice of the mixed crystal layer in the PVD layer system has a corundum structure, which is characterized by at least three lines associated with the corundum structure in a spectrum of the mixed crystal layer, measured by means of X-ray diffractometry. A vacuum deposition method for the production of a mixed crystal layer of a polyoxide and accordingly coated tools and components are also disclosed.

Layer system having at least one mixed crystal layer of a polyoxide

PROBLEM TO BE SOLVED: To improve defects in prior art, and provide a coating system suitable for high-temperature use including oxide coating having thermal stability, and a workpiece particularly a tool and a component protected by the coating systemSOLUTION: A PVD coating system for coating a workpiece contains at least one double oxide mixed crystal coating Composition of the double oxide is (Me1Me2)O At this point, Me1 and Me2 are severally at least one element out of Al, Cr, Fe, Li, Mg, Mn, Nb, Ti, Sb and V Elements Me1 and Me2 are different from each other A crystal lattice of mixed crystal coating in the PVD coating system has a corundum-type structure The corundum-type structure has at least three lines specific to the corundum-type structure in the spectrum of the mixed crystal coating measured by X-ray diffraction

Coating system having at least one double oxide mixed crystal coating

FIELD: metallurgy ^ SUBSTANCE: laminated system contains at least one layer of mixed crystals of a multicomponent oxide of the following composition (Me11-xMe2x)2O3, where each of Me1 and Me2 means at least one of the elements Al, Cr, Fe, Li, Mg, Mn, Nb, Ti, Sb or V, and thus elements Me1 and Me2 differ from each other In this case, the crystal lattice of the mixed crystals layer has a structure of a corundum, which is characterised by at least three, preferably four, in particular, five lines attributed to the structure of corundum in the spectrum of a layer of the mixed crystals, as measured by X-ray diffraction ^ EFFECT: improved thermal and chemical resistance of the coating ^ 48 cl, 7 dwg, 8 tbl, 1 ex

Michael Ante

Papers

Pulse enhanced electron emission (P3e™) arc evaporation and the synthesis of wear resistant Al–Cr–O coatings in corundum structure

Layer system with at least one mixed crystal layer of a multi-oxide

Layer system having at least one mixed crystal layer of a polyoxide

Coating system having at least one double oxide mixed crystal coating

Laminated system with layer of mixed crystals of multicomponent oxide