%0 Journal Article %A Valette, S. %A Denoirjean, Alain %A Danoix, R. %A Lefez, B. %A Hannoyer, B. %A Lefort, Pierre %A Fauchais, Pierre %D 2004 %I Begell House %N 2 %P 245-252 %R 10.1615/HighTempMatProc.v8.i2.90 %T ALUMINA-COATED STEEL: ROLE OF A MAGNETITE INTERPHASE ON THE ADHESION OF THE COATINGHT %U https://www.dl.begellhouse.com/journals/57d172397126f956,6c962d843dc35b18,4af23c5003659c42.html %V 8 %X To improve the adhesion of alumina coatings on low carbon steel, it is necessary to develop an oxide layer with a controlled thickness and chemistry at its surface. The best results were obtained with a wustite layer. The Wustite layer (Fe1-xO) is developed on a smooth low carbon iron substrate by its oxidation within a furnace under a pure CO2 atmosphere. However, before spraying, a preheating of the substrate and thus of its oxide surface by the plasma is mandatory in order to eliminate condensates and adsorbates. This step of the process induces more or less the transformation of wustite into magnetite (Fe3O4).
The purpose of this paper is the study of the influence of the magnetite phase and of the thickness of the oxide layer on the adhesion of Al2O3 coatings. The results show that the control of the oxide layer thickness is very important for a good adhesion which is probably linked to the cohesion of the layer. Below a critical thickness of the oxide layer the rapture of the coating is adhesive (at the interface alumina-iron oxide). Over it is a cohesive rupture inside the oxide layer. The composition of the oxide plays a role that is not still completely clarified, but the physico-chemical continuity of the phases present in the interfacial zone seems to be a crucial point. %8 2004-06-01