The Effect of Pt Content on the Scale Development on β-NiAl at Very Early Oxidation Stages

Very early stages of development of the oxide scale formed in air at 1150° on unmodified and containing varying amounts of Pt (5, 10 and 15 at.%) β-NiAl intermetallic compound were studied. The scale morphology was observed using scanning electron microscopy, while photoluminescence spectroscopy was applied to determine its phase composition with spatial resolution down to 1 μm. It was found that the scales were non-uniform in terms of their morphology and, to a lesser extent, of their phase composition. Pt additions resulted in earlier development of the α-Al 2 O 3 oxide, which, based also on recently reported literature experimental and modelling results, may be attributed to the increased rate of the scale evolution. The possible direct effect of Pt on the phase transformation of unstable aluminium oxides into α-Al 2 O 3 still needs to be verified as the complementary or alternative explanation.