Influences of W and Al on the Microstructure and Stress-Rupture Property of Re-Free Ni-Based Single Crystal Superalloys

The influence of W and Al on the solidus and liquidus temperatures, microstructure and stress-rupture property at 980 °C/250 MPa was investigated in three Re-free experimental Ni-based single crystal superalloys. The results indicated that the solidus temperature increased for 14.0 °C and 9.8 °C by adding 0.84 wt.% W only and adding 0.45 wt.% Al and 0.44 wt.% W to the base alloy, respectively. The γ′ morphology changed from nearly cuboidal in the base alloy to cuboidal by adding 0.45 wt.% Al and 0.44 wt.% W. The volume fraction of γ′ precipitates increased, while the γ channel width decreased after adding Al and W. The additions of Al and W improved the stress-rupture life at 980 °C/250 MPa because of higher γ′ volume fraction, narrower γ matrix channel and more complete rafting structure.