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Platinum Metals Rev., 1985, 29, (2), 56

The Behaviour of Platinum-Enriched Superalloys

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The continuing development of the gas turbine engine results in an associated demand for improved materials from which critical components can be fabricated. These materials must be capable of providing not only the necessary creep strength at elevated temperatures but also adequate resistance to cyclic oxidation and hot corrosion.

With conventional superalloys, compositional changes made to improve the mechanical properties may result in inferior resistance to high temperature oxidation and corrosion. However, enhanced resistance can be obtained by enriching nickel based superalloys with platinum. An examination of the microstructures that form when platinum is added to superalloys has been conducted by Dr. G. J. Tatlock and T. J. Hurd, of the University of Liverpool who have compared, in their oxidised and hot corroded forms a conventional superalloy with another which had 4.5 per cent of platinum substituted for some of the nickel. The results of their oxidation investigations have now been published (Oxid. Met., 1984, 22, (5/6), 201–226).

Morphological studies confirm that the two alloys behave in a very similar way at 900°C, but that at 1100°C notable differences occur. At the higher temperature platinum appears to have a small but significant effect on the diffusion of the other elements present in the alloy. By a complex sequence of events, this results in the formation of a protective alumina scale which provides the platinum-containing alloy with a distinct improvement in oxidation resistance.

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