Potential of IrAl base alloys as ultrahigh-temperature smart coatings

For developing ultrahigh-temperature oxidation-resistant coatings, phase co nstitution and stability, fabrication methods, mechanical properties, therm al expansion and oxidation behavior are discussed for B2 IrAl alloys. Effec ts of ternary additions (Ni, Co and Fe) on oxidation behavior are also desc ribed. For practical use of ultrahigh-temperature coatings, an effective ox ygen diffusion barrier (ODB) is required for the heart,of multilayered ultr ahigh-temperature coatings and Ir has promise to be ODB. A problem in using Ir is a formation of gaseous oxide; IrO3, over 1395K. This can be overcome by alloying with Al. Recently we have found that, by oxidation, IrAl-base alloys form smart and self-healing multifunctional layered structures compo sed of (1) continuous Ir layer as ODB and (2) continuous Al2O3 layer to pro tect ODB. In this paper, several characteristics of IrAl alloys are describ ed and potential of IrAl as smart oxidation resistant coatings is discussed : (C) 2000 Elsevier Science Ltd. All rights reserved.