Effects of Zirconium Additions on the Microstructure and Stress-Rupture Properties in Polycrystalline Ni-Based Superalloys

In the present work, comprehensive investigations were conducted to examine the distribution behavior of the minor alloying elementMinor-alloying element Zr, its impact on microstructural evolutionMicrostructural evolution and effect on the high-temperatureHigh temperaturestress-rupture propertiesStress-rupture properties in IN 100 superalloysSuperalloys. The results indicate that the presence of Zr influences the eutectic phase in as-cast alloys, resulting in a reduction in the γ channel width and an increase in both the volume fraction and size of the γ′ phase. Through the time of flight-secondary ion mass spectrometry and transmission electron microscope analysis, Zr is found to segregate along the eutectic front in the form of Ni₅Zr in 900 °C stress-ruptured samples, rendering IN 100 alloys enhanced creep resistanceCreep resistance at elevated temperatures. Heat treatmentHeat treatment at 1200 °C could effectively eliminate the eutectic structure, thus mitigating the segregationSegregation of Zr. A maximum endurance life in IN 100 alloys at 900 °C/314 MPa and 950 °C/225 MPa is reached when Zr content is approximately 700 ppm. Synergistic effects including the eutectic content, volume fraction, and the degree of raftingRafting of the γ′ phase together with the dislocation networkDislocation networks structure were analyzed and discussed, contributing to the improved stress-rupture propertiesStress-rupture properties in IN 100 alloys.