Strategic elimination of gas-entrapped lack-of-fusion in laser beam powder bed fusion alloy via liquid-induced healing

A critical challenge impeding broader application of metal additive manufacturing lies in the process-induced defects that compromise the structural integrity and mechanical properties of fabricated components. Among these, lack-of-fusion (LoF) defects are the most prevalent, characterized by gas entrapment, large volumes, and irregular morphologies. This work reports a fundamental process advancement: the liquid-induced healing (LIH) technique uniquely integrates buoyancy-driven gas expulsion with controlled grain coarsening to simultaneously eliminate defects and enhance high-temperature performance in laser beam powder bed fusion components. Using laser beam powder bed fusion fabricated IN718 as the demonstration alloy, we systematically evaluate the defect healing mechanism and its effects on microstructure and mechanical properties. The results show that LIH increases the relative density from 97.99 % to 99.97 % and improves tensile elongation at 650°C by 1.8 times, with only an approximate 10 % reduction in material strength. Notably, the fatigue performance (25°C, σ_max = 950 MPa) demonstrates a 3.4 times extended lifetime. More importantly, the creep life (650°C, 650 MPa) increases by 6.5 times owing to the simultaneous defect healing and microstructure regulation. The fundamental advancement is LIH’s integrated remelting mechanism that concurrently enables gas evacuation and microstructural optimization, establishing a new pathway to heal defects while decisively addressing the long-standing creep life deficiency in laser beam powder bed fusion components.