An assessment of the oxidation resistance of an iridium and an iridium/platinum low-activity aluminide/MarM002 system at 1100 degrees C

Platinum-aluminide coatings provide excellent protection for turbine blades against the aggressive environments in which modern aero-gas turbines oper ate. However, there is an increasing interest in the modification of alumin ide coatings with other noble metals, such as iridium. This study assessed the oxidation performance of an iridium-aluminide and an iridium/platinum-a luminide on MarM002 substrates. The coatings were isothermally soaked at 11 00 degrees C and analysed using optical, SEM and XRD techniques, with their performance being gauged against that of a low-activity platinum-aluminide . Both of the iridium systems offered a lower level of performance than tha t afforded by the platinum-aluminide, This paper will discuss the mechanism s of degradation of these coating systems and address the scale growth and adherence. (C) 1999 Elsevier Science S.A. All rights reserved.