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Investigations of the deuterium permeability of as-deposited and oxidized Ti2AlN coatings

: Gröner, L.; Mengis, L.; Galetz, M.; Kirste, Lutz; Daum, P.; Wirth, M.; Meyer, F.; Fromm, A.; Blug, B.; Burmeister, F.

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Materials 13 (2020), Nr.9, Art. 2085, 9 S.
ISSN: 1996-1944
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IWM ()
Fraunhofer IAF ()
MAX phase; Ti2AlN; PVD coating; oxidation; hydrogen permeation

Aluminum containing Mn+1AXn (MAX) phase materials have attracted increasing attention due to their corrosion resistance, a pronounced self-healing effect and promising diffusion barrier properties for hydrogen. We synthesized Ti2AlN coatings on ferritic steel substrates by physical vapor deposition of alternating Ti- and AlN-layers followed by thermal annealing. The microstructure developed a {0001}-texture with platelet-like shaped grains. To investigate the oxidation behavior, the samples were exposed to a temperature of 700 °C in a muffle furnace. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) depth profiles revealed the formation of oxide scales, which consisted mainly of dense and stable α-Al2O3. The oxide layer thickness increased with a time dependency of ~t1/4. Electron probe micro analysis (EPMA) scans revealed a diffusion of Al from the coating into the substrate. Steel membranes with as-deposited Ti2AlN and partially oxidized Ti2AlN coatings were used for permeation tests. The permeation of deuterium from the gas phase was measured in an ultra-high vacuum (UHV) permeation cell by mass spectrometry at temperatures of 30–400 °C. We obtained a permeation reduction factor (PRF) of 45 for a pure Ti2AlN coating and a PRF of ~3700 for the oxidized sample. Thus, protective coatings, which prevent hydrogen-induced corrosion, can be achieved by the proper design of Ti2AlN coatings with suitable oxide scale thicknesses.