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Open Access item Aluminium depletion in NiCrAlY bond coatings by hot corrosion as a function

Authors:Mayoral Gastón, María del Carmen
Andrés Gimeno, José Manuel
Bona, M. T.
Higuera, V.
Belzunce, F. J.
Keywords:NiCrAlY bond coats, Hot corrosion, Al depletion, HVOF, HFPD
Issue Date:Feb-2008
Citation:Surface & Coatings Technology 202 (2008) 1816–1824
Abstract:Three different projection system are used to prepare NiCrAlY bond coats over metallic substrates: atmospheric plasma spray (APS), high velocity oxyfuel (HVOF) and high frequency pulse detonation (HFPD). These coatings were tested in hot corrosion experiments with sprayed Na2SO4 at 1000ºC for 20 and 100 hours experiments in air. Coatings surface composition after thermal treatment was characterised by XRD and SEM. Cross section of coatings were analysed by SEM-EDX. A relationship between microstructural characteristics of initial coatings and final performance in hot corrosion was found in terms of porosity percentage: plasma sprayed coatings present higher percentage of porosity compared to HVOF and HFPD projection systems for the same composition and Al is heavily consumed in interparticle oxidation. This Al depletion in turn involves intrinsic chemical failure and surface layer is comprised by a porous spinel of mixed oxides. On the other hand, high energy projection systems produce dense coatings allowing the Al migration to external alumina layer, particularly in the case of HVOF coating.
Description:Journal home page: http://www.elsevier.com/wps/find/journaldescription.cws_home/504101/description#description
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