Research progress of hafnium effects on cracking formation, microstructure, and high-temperature mechanical properties of high-strength nickel-based superalloys prepared by additive manufacturing

Nickel-based superalloys have the outstanding load-bearing and high-temperature resistance properties, which are widely used as the key structural materials for the hot-end components of aerospace equipment. However, the traditional high-strength nickel-based superalloys are prone to the crack formation characterized by strong constraints and rapid non-equilibrium solidification during additive manufacturing process, severely limiting the application. The non-equilibrium segregation of key alloying elements at the end of solidification is the main factor affecting crack formation. For the typical difficult-to-print γ′-strengthened nickel-based superalloys (CM247LC), the hafnium element (Hf) has significant impact on the solid-liquid phase line temperature difference. The distribution characteristics and crack sensitivity influence of Hf element in additive manufacturing nickel-based superalloys were analyzed in this paper, the influence of Hf element on the microstructure evolution of typical high-strength nickel-based superalloys was discussed during heat treatment, and the effect of Hf element on the high-temperature mechanical properties of high-strength nickel-based superalloys in additive manufacturing was summarized.