Exceptional creep resistance achieved by precipitate and grain boundary strengthening in a modified additively manufactured nickel-based superalloy

In this study, a modified GH4169 superalloy, designated GH4169-CoZr, was designed via computational alloying. Then, specimens of the GH4169 and GH4169-CoZr superalloys were produced via laser directed energy deposition (DED), and their high-temperature creep behavior was comparatively investigated at 595 °C and 825 MPa via creep testing, microstructural characterization, and simulation. Experimental results demonstrated that GH4169-CoZr superalloy has better creep life. The enhanced creep resistance is attributed primarily to a reduction in Laves phase content, combined with grain-boundary strengthening due to Zr segregation. In addition, precipitation strengthening plays a key role, as evidenced by the distinct γ′/γ″ precipitates in GH4169-CoZr, with an average size of approximately 27 nm and a volume fraction of about 31%, which enhances both order strengthening and modulus strengthening. Moreover, the GH4169-CoZr superalloy exhibits a lower stacking fault energy (SFE) compared to GH4169 (151.9 mJ/m 2 vs. 156.8 mJ/m 2 ), which restricts dislocation cross-slip and hinders dislocation climb. Therefore, these synergistic effects of these microstructural characteristics collectively contribute to the superior creep resistance of GH4169-CoZr superalloy. This advancement improves high-temperature creep resistance, broadening composition design and microstructure concepts for future superalloy development.