Failure behaviour of functionally gradient materials under thermal cycling conditions

Functionally gradient coatings are coating systems, which are used to increase performances of high temperature components in the hot gas turbine section of gas turbine engines, diesel engines, in aerospace and aircraft applications. These coatings consist of a transition from the metallic bond layer to cermet and from cermet to the ceramic layer. Functionally gradient materials were applied on stainless steel substrates via an atmospheric plasma spray technique. The coating architecture was NiCrAl, 75% NiCrAl + 25% MgZrO₃, 50% NiCrAl + 50% MgZrO₃, 25% NiCrAl + 75% MgZrO₃ and 100% MgZrO₃ layers, respectively. The FGM samples were thermally cycled at temperature range of 47 and 600 °C for periods of 303 s and then characterised by optical microscopy, image analyser, SEM and XRD. Microhardness of the layers was measured using a standard microhardness tester. The obtained results are presented.