The Effects of Energy Density and Heat Treatment on the Properties of 3D Printed Tungsten

In the realm of Selective Laser Melting (SLM), a substantial temperature gradient gives rise to rapid thermal fluctuations, which, in turn, engender heightened residual stresses and microcracking—constituting critical obstacles in the additive manufacturing of tungsten (W) materials. The volumetric energy density emerges as a pivotal parameter influencing the density of pristine W structural components fabricated via SLM. The endeavor to eliminate defects in the fabricated parts solely through the optimization of SLM process parameters has been found to be arduous. To this end, crystalline W powder with a narrow grain size distribution was employed as the feedstock, and the implementation of substrate preheating was explored to fabricate W structural components featuring a lattice structure using SLM. Subsequently, the produced specimens underwent heat treatment at temperatures of 1100 ℃, 1400℃, 1700 ℃, and 1900 ℃ for a duration of 2 h. The mechanical properties and microstructures of the specimens subjected to heat treatment at varying temperatures were meticulously investigated. The results indicate that an optimal volumetric energy density of approximately 972 J/mm³ is necessary to achieve a theoretical density of 96.2%. Following heat treatment at 1700 ℃, the samples exhibited superior mechanical properties, with ultimate compressive strengths and microhardness values reaching 1200 MPa and 457HV, respectively. The fracture morphology displayed features of cleavage fracture, and the microcracks were largely mitigated after heat treatment at 1700 ℃, suggesting enhanced metallurgical bonding between the layers and particles.