Abstract
Conversion coatings modified by deposits of alumina, with or without zirconium, calcium, or strontium additions, have been studied as a way of improving the thermal oxidation resistance of a 17Cr ferritic stainless steel. Conversion coatings, characterised by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. After heating, the coatings present a continuous composition gradient with refractory compounds at the surface. The influence of added elements (Zr, Ca, or Sr) on the behaviour of the alumina coating was investigated at 1000°C. Calcium improved the protective character of the alumina coating. The morphology and chemical composition of the different deposits were also analysed and results on the thermal stability of such coatings on Fe–17Cr ferritic stainless steel are presented.
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