Oxidation behaviour of functionally gradient coatings including different composition of cermets

Functionally gradient coatings are coating systems which are used to increa se performances of high temperature components in the hot gas turbine secti on of gas turbine engines, diesel engines, in aerospace and aircraft applic ations. These coatings consist of a transition from the metallic bond layer to cermet and from cermet to the ceramic layer. In this study, oxidation b ehaviour of functional gradient coatings produced by plasma-spray on AISI 3 04 L stainless steel substrates was investigated. The plasma spray process was employed to deposit metallic, cermet and ceramic powders such as NiCrAl , NiCrAl + MgZrO3 and MgZrO3 on the substrate. A certain cermet composition for each sample was selected. Oxidation tests were carried out at temperat ures of 800 and 1000 degreesC. The coatings and oxidised coatings were exam ined by means of an optical microscope, SEM and X-ray diffractometry. The r esults showed that the oxide film thickness and oxidation rate at 1000 degr eesC are considerably higher than at 800 degreesC. (C) 2001 Elsevier Scienc e B.V. All rights reserved.