Creep-Rupture Life And Alloy Manufacturing Criterion Related To The Solidification And Precipitation Temperatures In Nickel-Based Single-Crystal Superalloys

The solidification and precipitation temperatures were measured and were correlated with the creep-rupture property and the microstructure of nickel-based single crystal superalloys. For three Co-content varying Ni-10 mol% Cr-12 mol% Al-1.5 mol% Ti-Ta-W-Mo-0.25 mol% Re-0/4.5/9.0 mol% Co alloys and also for three Cr-content varying Ni-10/13/16 mol% Cr-12 mol% Al-1.2 mol%Ti-Ta-W-Mo alloys, the liquidus, solidus, eutectic gamma' precipitation and gamma' solvus temperatures were determined by differential thermal analysis (DTA). It was found that as the Co and Cr contents increased, the gamma' solvus temperature decreased and there was the attendant decrease in the volume fraction of the gamma' phase in the alloys. In response to these changes the creep-rupture lives decreased with the Co and Cr contents. These results imply that the gamma' solvus temperature is an indication of the creep-rupture lives of the nickel-based superalloys. In addition, a manufacturing condition for single-crystal growth was estimated from the measured solidification temperature range of alloys. All of the six alloys were shown to meet this condition, and their single crystals were grown successfully in agreement with the estimation.