Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température
J. Phys. IV France 03 (1993) C9-123-C9-131
The oxidation mechanism of Pt20Ni30Al50P.A. van Manen1, G.W.R. Leibbrandt2, R. Klumpes1 and J.H.W. de Wit1
1 Delft University of Technology, Laboratory for Materials Science, Div. Corrosion Technology and Electrochemistry, Rotterdamseweg 137, 2628AL, Dleft, the Netherlands
2 University of Utrecht, Department of Atomic and Interface Physics, P.O. Box 80 000, 3508 TA, Utrecht, the Netherlands
Additions of platinum to aluminium oxide forming alloys are known to imporve their high temperature corrosion resistance. This is known as the "precious metal effect". In this study the effect of platinum on the oxidation mechanism was investigated by comparing the oxidation mechanism of β-NiAl and Pt20Ni30Al50. This composition agrees with the average composition of a platinum modified aluminide coating. The alloys were oxidized at temperatures from 1000 to 1200°C. The growth of the oxide scale on the NiAl alloy proceeds both by aluminium and by oxygen diffusion through the scale resulting in growth within the scale. However, on Pt20Ni30Al50 the growth of the scale is limited to the oxide/gas interface due to a predominant aluminium transport through the scale. Therefore the growth stresses are reduced. Another difference is the extensive void formation at the β-NiAl/oxide interface. This was not observed on the Pt20Ni30Al50 samples. The phenomena mentioned above are the two likely reasons for the improved oxide scale adherence.
© EDP Sciences 1993