Optimizing Selective Laser Melting of a High-Alloyed Ni-Based Superalloy: Achieving Crack-Free Fabrication with Enhanced Microstructure and Mechanical Properties

Abstract

Selective laser melting, a predominant additive manufacturing technology for fabricating geometrically complex components, faces significant challenges when processing high-performance Ni-based superalloys containing elevated Al and Ti concentrations (typically > 6 wt%), particularly regarding micro-cracking susceptibility. In this study, we demonstrate the successful fabrication of a novel crack-free Ni-based superalloy with 6.4 wt% (Al + Ti) content via optimized energy density, systematically investigating its microstructure, defects, and mechanical properties. Process parameter analysis revealed that insufficient energy densities led to unmolten pores, while excessively high energy densities caused keyhole formation. With an optimal energy density of 51.1 J/mm³, the crack-free superalloy exhibited exceptional mechanical properties: room temperature tensile strength of 1130 MPa with 36% elongation and elevated-temperature strength reaching 1198 MPa at 750 °C. This strength enhancement correlates with the precipitation of nanoscale γ′ phases (mean size: 31.56 nm) during high temperature. Furthermore, the mechanism of crack suppression is explained from multiple aspects, including energy density, grain structure, grain boundary characteristics, and the distribution of secondary phases. The absence of low-melting-point eutectic phases and brittle phases during the printing process is also explained from the perspective of alloy composition. These findings provide a comprehensive framework for alloy design and process optimization in additive manufacturing of defect-resistant Ni-based superalloys.