Nano‐NbC‐Induced Microstructural and Mechanical Improvements in GH4099 Nickel‐Based Superalloys

The study systematically incorporates nano‐NbC particles into GH4099 nickel‐based superalloys to improve their microstructural characteristics and high‐temperature mechanical properties. The introduction of nano‐NbC substantially refines grain structure, facilitating a transition from columnar‐to‐equiaxed microstructures and promoting the formation of finer MC‐type carbides. This results in significant enhancements in strength, creep resistance, and thermal stability of the alloy. Mechanical testing conducted at both room temperature and 800 °C demonstrates that adding 1.0 wt% nano‐NbC increases tensile strength by 14.3% and yield strength by 19.5%. However, this enhancement comes at the cost of reduced ductility. An excessive concentration of nano‐NbC (2.0 wt%) leads to carbide agglomeration, which adversely affects both strength and ductility. Transmission electron microscopy analysis reveals excellent interfacial bonding between the MC carbides and the alloy matrix, which enhances load transfer efficiency and thereby improves mechanical properties. These findings suggest that GH4099 superalloys, when enhanced with optimal amounts of nano‐NbC, are promising for advanced applications requiring high‐temperature structural integrity.