Gas turbine engines are widely used for both stationary and mobile applications, and the turbine blades, which are highly stressed during service, are required to operate at high temperatures in oxidising atmospheres which may be contaminated with corrosive fuel residues and ingested salts. To some extent nickel-based superalloy turbine components can be protected against both oxidation and hot corrosion by nickel aluminide diffusion coatings, but in more severe environments the protective coating may break down, reducing service life.

The development of platinum-containing coating systems has been reported here on several occasions over the past decade as materials scientists have sought both to improve the protection given by such coatings and to establish the precise role of the platinum in the process.

A further contribution on the subject has been published recently (H. M. Tawancy, N. M. Abbas and T. N. Rhys-Jones, Surf. Coat. Technol., 1991, 49, (1–3), 1–7).

Following an investigation of the microstructure of platinum-modified aluminide coatings on selected nickel-based superalloys, the authors identify a number of ways by which the platinum improves the protective ability of the coating. Oxidation behaviour depends upon the composition of the superalloy substrate, especially on its rare earth content.