TiAIN based nanoscale multilayer coatings designed to adapt their tribological properties at elevated temperatures

The addition of properly selected elements, coupled in nanoscale multilayer structures, can further enhance the properties of TiAlN coatings and bring new high performance. The incorporation of Y in the nanoscale pseudo-superlattice TiAlCrN/TiAlYN with typical period of 1.7 nm not only improves the oxidation resistance but also effectively reduces the coefficient of friction of the coating from 0.9 to 0.65 at temperatures in the range of 850–950 °C. The adaptation of the tribological properties occurs as a result of the preferential migration of the Y to the column boundaries. TiAlN/VN superlattice can achieve another self-adaptation process. During friction the coatings adapt themselves to the combined thermal and mechanical wear by the formation of highly lubricious vanadium-oxides due to high flash temperatures at the asperity contacts on the surface. The integrity of the bulk of the coating is retained, leading to exceptionally low, for superhard coatings, friction coefficient of 0.5 and a wear coefficient of 2 × 10−17 m3·N−1·m−1. The coatings have been deposited by the combined steered cathodic arc unbalanced magnetron sputtering method.</p

TEM-EELS study of low-friction superlattice TiAlN/VN coating: the wear mechanisms

A 20-50 nm thick tribofilm was generated on the worn surface of a multilayer coating TiAlN/VN after dry sliding test against an alumina counterpart. The tribofilm was characterized by applying analytical transmission electron microscopy techniques with emphasis on detailed electron energy loss spectrometry and energy loss near edge structure analysis. Pronounced oxygen in the tribofilm indicated a predominant tribo-oxidation wear. Structural changes in the inner-shell ionization edges of N, Ti and V suggested decomposition of nitride fragments

Nanostructural separated TiN-based protective coatings

The results of the investigations of the physical mechanical and operational characteristics of the multicomponent (Ti,Zr)N coatings, generated by physical vapor deposition from the separated plasma flows are presented

Epitaxial growth of Al-Cr-N thin films on MgO(111)

Cubic rock salt structure Al0.60Cr0.40N and Al0.68Cr0.32N films of different thicknesses were grown epitaxially onto MgO(111) substrates by reactive unbalanced magnetron sputtering at 500°C. Rutherford backscattering spectroscopy reveals stoichiometric nitrides with Al/Cr ratios close to the ones of the used compound targets of 60/40 and 70/30. High resolution x-ray diffraction proves epitaxial growth over the whole film thickness up to thicknesses of ~1.8 µm. Reciprocal space maps and selected area electron diffraction show that the AlxCr1-xN films grow fully relaxed. Scanning and transmission electron microscopy imaging reveals columnar microstructures with column widths between 12–16 nm and {001} surface faceting on individual columns. The fully relaxed growth and the columnar structure can be attributed to limited ad‑atom mobility on the initial AlxCr1-xN(111) growth surface.Original publication: H. Willmann, M. Beckers, J. Birch, P.H. Mayrhofer, C. Mitterer, and L. Hultman, Epitaxial growth of Al-Cr-N thin films on MgO(111), 2008, Thin Solid Films, (517), 2, 598-602.http://dx.doi.org/10.1016/j.tsf.2008.07.003. Copyright: Elsevier B.V., http://www.elsevier.com