Effect of Y2O3 contents on oxidation resistance at 1150 °C and mechanical properties at room temperature of ODS Ni-20Cr-5Al alloy

Ni-20Cr-5Al alloy with Y2O3 addition (i.e., 0, 0.2, 0.4, 0.6, 0.8, 1.0, 3.0 and 5.0 wt%) are used to prepare oxide dispersion strengthening (ODS) Ni-based superalloy by powder metallurgy technology. The effect of Y2O3 particles on oxidation resistance at 1150 °C and mechanical properties at room temperature of Ni-20Cr-5Al alloy was investigated. The results show that the oxidation resistance of alloys is improved when the content of Y2O3 is under 0.6 wt%. The oxidation resistance of alloys decreased obviously when the content of Y2O3 is over 0.8 wt%. It is due to the small amount of Y2O3 is conducive to form stable oxide scale, and improves the adhesion of oxide scale and matrix. While Y2O3 content is too high, it is easier to result in segregation of Y2O3, which create defects in matrix and decrease exfoliation resistance of oxide scale. Continuous and compact Al2O3 oxide scale can effectively protect matrix. The relative density of alloys can be significantly increased with Y2O3 addition which is 0.2-0.6 wt%, it's speculated that distribution of Y2O3 in matrix is benefit to promote rearrangement and densification of grains during process of sintering. While Y2O3 content is more than 0.8 wt%, Y2O3 will hinder viscous flow and reduce relative density due to its strong thermal stability.