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

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. •Role of Ti on the oxidation behaviour of a low-density Co-Ni-Al-Cr-Ta-Ti superalloy is presented.•Increment from 2 at% to 4 at% Ti improved the resistance at 800 ºC, 900 ºC and 950 ºC.•γ(fcc)-matrix of 4 at% Ti have higher Ni and Al content allowing thick alumina barrier.