On the role of Ti aiding the protective barrier layer formation for γ′(L12)-strengthened Co-30Ni-10Al-5Cr-2Ta-2/4Ti superalloys

Abstract The paper reports the influence of Ti on the oxidation behaviour of a new class of low-density L12-strengthened Co-Ni-Al-Ta-Cr-Ti alloys. Oxide scales following the isothermal exposure for 1000 h at 800 °C, 900 °C, and 950 °C were characterized. Contrary to the expectation, increasing Ti content from 2 at.% Ti to 4 at.% Ti promotes significant oxidation resistance at all temperatures. The varying amount of Ti does not affect the overall sequence of oxide layers and phase chemistry but does affect the kinetics of the barrier layer formation. Two plausible reasons are discussed for the beneficial effect of Ti addition.