Quasicrystals, materials with ordered but non-periodic atomic structure, have attracted considerable attention due to their unique physical and chemical properties. Among them, Al–Cu–Fe-based alloys, in particular Al–Cu–Fe–Cr, exhibit high hardness, corrosion resistance, and low friction coefficient. The production of coatings based on them opens up prospects for a wide range of applications, including wear-resistant coatings, thermal barrier layers, and catalytic materials.
Physical vapor deposition (PVD) is a versatile technology for depositing thin films and coatings of varying composition and structure. PVD processes such as magnetron sputtering, electron beam evaporation, and arc evaporation allow control over the composition, structure, and morphology of the resulting coatings by varying deposition parameters such as substrate temperature, gas pressure, and deposition rate.
An innovative method for producing quasicrystalline and approximant layers of Al–Cu–Fe–Cr and Al–Cu–Fe by physical vapor deposition (PVD) is presented. The initial powder mixtures of a given composition were vacuum pressed at 400 °C in a graphite mold to form sputtering targets with a density of about 50%. X-ray analysis of the used targets showed the presence of Al and Cu, as well as significant amounts of intermetallic compounds θ (Al2Cu) and/or λ (Al13Fe4).
These targets were used to deposit 10 μm thick preliminary layers on alumina substrates. Decagonal approximant layers, predominantly of the O1 type, were obtained by sputtering from an Al–Cu–Fe–Cr target followed by vacuum annealing in an argon atmosphere at 500 °C for 4 h. Icosahedral and rhombohedral approximant phases were synthesized by sputtering from an Al–Cu–Fe target and annealing in argon at 850 or 450 °C, respectively.
Various approaches are used to obtain quasicrystalline and approximating Al–Cu–Fe–Cr and Al–Cu–Fe coatings by PVD. One of them is deposition from a multicomponent target containing the elements Al, Cu, Fe and Cr in the required proportions. Another approach is to use several targets, each consisting of one or more elements, and to simultaneously deposit atoms from each target. Controlling the ratio of atomic flows from different targets allows precise regulation of the composition of the resulting coating.
The obtained coatings are examined using various methods, such as X-ray diffraction, scanning electron microscopy and atomic force microscopy, to determine their structure, morphology and composition. The mechanical properties of the coatings, such as hardness and elastic modulus, are assessed using nanoindentation. The corrosion resistance of the coatings is studied using electrochemical methods.
Author: M. J. Daniels, D. King, L. Fehrenbacher, J. S. Zabinski, J. C. Bilello
Institute: Office of Technology Assessment and Transfer, 133 Defense Highway, Suite 212, Annapolis, Maryland 21401, USA, Air Force Research Laboratory, 2941 P. Street, Wright-Patterson AFB, Ohio 45433, USA, Center for Nanomaterials Science, Department of Materials Science and Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109-2136, USA