Microstructural Evolution and Phase Characterization of a Ni-Based Superalloy Under Laser-Assisted Heat Treatment

This study investigates the microstructural evolution and mechanical behavior of a Ni-based superalloy subjected to combined heat treatment and laser processing. Quantitative analysis of γ′ Ni3(Al,Ti) and η (Ni3Ti) phase distributions were performed using SEM-based statistical methods. The results show that γ′ precipitates exhibit a fine and uniform distribution with sizes in the range of ~0.05–0.30 µm and a high number density (n ≈ 2916), whereas the η (Ni3Ti) phase appears as relatively coarse particles (~0.1–0.6 µm) with lower number density (n ≈ 505). Laser treatment promotes redistribution of γ′ precipitates and suppresses η phase formation, resulting in improved microstructural homogeneity. Mechanical characterization reveals that optimal aging (2 h) yields the highest hardness of ~525 HV at 300 °C, while tensile properties show yield strength in the range of ~1000–1150 MPa and ultimate tensile strength of ~1300–1500 MPa. The results demonstrate a strong correlation between γ′ refinement and enhanced mechanical performance. These findings provide a quantitative understanding of phase evolution and establish a microstructure-property relationship for optimizing Ni-based superalloys.