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%0 Thesis
%A Naji, Ammar
%T Design of Al diffusion coatings for Fe-based and Ni-based alloys; 1st ed.
%V 16
%I RWTH Aachen University
%V Dissertation
%C Aachen
%M RWTH-2018-227226
%@ 978-3-8440-6204-5
%B Schriftenreihe des DECHEMA-Forschungsinstituts
%P XII, 117 Seiten : Illustrationen
%D 2018
%Z Zweitveröffentlicht auf dem Publikationsserver der RWTH Aachen University
%Z Dissertation, RWTH Aachen University, 2018
%X Components, which consist of metallic materials and operate at high temperatures, can degrade due to high temperature corrosion attack. The most frequently occurring phenomenon is oxidation. When metallic materials are exposed to an oxidizing atmosphere, it is desired that elements, which are called protective oxide forming elements, diffuse from the material interior to the material surface and form a dense and slow-growing oxide scale, which acts as a diffusion barrier and decelerates further oxidation. Since for several reasons most high temperature alloys contain only a limited amount of protective oxide forming elements, coatings are applied with higher amount of these elements. The concept of the diffusion coatings is to enrich the substrate surface with one or more protective oxide forming elements (e.g. Al). Aluminization of Fe- and Ni-based alloys leads to Al diffusion coatings, which can consist of one phase or several stacked phases, depending on the Al activity within the intermetallic phase, according to the Fe-Al and Ni-Al phase diagrams. In this work, the aim was to develop a predictive design procedure for the manufacturing of pack cementation Al coatings on austenitic steels and Ni-based alloys. The pack cementation process is a CVD (chemical vapour deposition) process, where the substrate to be coated is embedded in a powder mixture, consisting of the deposition element (e.g. Al), an activator (e.g. NH4Cl) and a filler (e.g. Al2O3) and is heated in a tube furnace for several hours in an Ar/5
%F PUB:(DE-HGF)3 ; PUB:(DE-HGF)11
%9 BookDissertation / PhD Thesis
%R 10.18154/RWTH-2018-227226
%U https://publications.rwth-aachen.de/record/730991