Characterization of Solidification Process and Defect Formation of K492M Superalloy

K492M nickel-based superalloy is a key material for hot-section components of aero-engines and gas turbines. Due to its high alloying degree and wide solidification temperature range, casting defects such as shrinkage porosity and inclusions readily occur during casting process, impairing the service performance of castings. In the present work, thermodynamic simulation combined with isothermal quenching tests were adopted to systematically investigate the solidification behavior, microstructure evolution, element segregation and precipitated phase formation of the alloy. Electron probe micro analyzer and energy dispersive spectroscopy were also used to analyze the phase composition and element distribution. The results reveal that three phase transformations take place in sequence during solidification, namely L→γ, L→γ+MC, and L→γ+γ′ eutectic phase, with the characteristic temperatures of 1345 ℃, 1310 ℃ and 1240 ℃ respectively. There is a significant element segregation during solidification: Co, Cr and W are enriched in dendritic trunks, while Mo, Ti and Ta tend to accumulate in inter-dendritic liquid phase. Two types of MC carbides with distinct morphologies are formed, exerting dual effects on liquid feeding and shrinkage cavity formation. Petal-shaped divorced (γ+γ′) eutectic phase forms in the late solidification stage, easily inducing porosity defects, which should be regulated by heat treatment. This work clarifies the complete solidification path and defect formation mechanism of K492M alloy, providing a theoretical basis for optimizing its casting process.