New insights into effects of Ru on the oxidation behaviour of Ni-based single-crystal superalloys at 1150 °C

This study provides new insights into Ru-effects on the oxidation resistance of some fourth-generation single-crystal Ni-based superalloys at 1150 °C. No apparent evaporation of Ru-oxides was observed. On the contrary, HCP-structured Ru-Re solid solution ((Ru,Re)ss) particles were found to be embedded in the oxide scale for the Ru-added alloys. Local evaporation of Re-oxides from the (Ru,Re)ss particles, as well as the internal stress at their boundaries, gives birth to micro-pores and cracks and increased the spallation of oxide scales upon cooling. Despite the inhibition of undesirable TCP phase precipitation, Ru additions degrade the high-temperature oxidation resistance of the alloys considerably.