Benefits of minor additions of yttrium to the oxidation and creep behaviour of a nickel-based composite

Abstract

Metal matrix composite materials produced by the directional solidification of eutectic alloys continue to be advocated as future turbine blade materials. However, although considerable improvements in creep performance have been obtained from some eutectic alloys, relative to current superalloys, their oxidation and corrosion resistances have failed to meet the requirements for engine applications. One such alloy, designated y-y'-Cr ₃ C ₂ , consisting of a nickel matrix reinforced by cubic y' precipitate particles and aligned Cr ₃ C ₂ fibres has been shown previously to have superior creep properties to current advanced superalloys at high temperatures (over 950 °C). However, the alloy is subject to severe surface degradation in cyclic oxidation conditions by the spallation of chromium-rich oxide scales and by internal oxidation