Effect of Laser Energy Density on Temperature Field, Forming Quality, and Performance of LPBF-Fabricated Nickel-Based Superalloy Composites

Laser energy density plays a crucial role in determining the forming quality, microstructure, and mechanical properties of components fabricated by laser powder bed fusion (LPBF). Hexagonal boron nitride (h-BN) reinforced Hastelloy X (HX) composites of 0.2 wt% have been proven to eliminate cracks by regulating the laser absorption behavior and the temperature field, thereby reducing the temperature gradient and carbide segregation. This approach synergistically enhanced both the strength and elongation of HX formed via LPBF. However, the lack of process optimization studies for this system has hindered its broader industrial application. This study investigated the effects of varying laser energy densities on 0.2 wt% h-BN/HX composites and identified the optimal laser processing parameter. Experimental results showed that an optimal laser energy density of 41.67 J/mm³ resulted in the best microstructure, characterized by fine grains (10.97 µm), high densification (99.81%), and low surface roughness (Sa = 4.68 µm). The mechanical properties, including ultimate tensile strength (1259.18 MPa) and elongation (18.26%), were also maximized at this energy density. Additionally, the optimal energy density improved microstructural uniformity, dislocation density (kernel average misorientation (KAM) = 0.64), and texture strength (Taylor factor = 3.18). This study provides valuable insights into the influence of laser energy density on thermal behavior, forming quality, and mechanical performance of LPBF-manufactured 0.2 wt% h-BN/HX, offering guidance for optimizing LPBF processing parameters and enhancing the performance of nickel-based composites in advanced engineering applications.