Laser Powder Bed Fusion of Pure Tungsten: Effects of Process Parameters on Morphology, Densification, Microstructure

Abstract

Tungsten has been widely used in many industrial fields due to its excellent properties. However, owing to its characteristics of inherent brittleness at room temperature and high melting point, it is difficult to prepare tungsten parts with high complexity via traditional methods. In the present work, tungsten samples were prepared by laser powder bed fusion. The influence of each process parameter including laser power, scanning speed, and hatch spacing on the surface morphology, densification, and microstructure of tungsten samples was systematically investigated. The results showed that the use of the appropriate parameters, especially high laser power, can effectively improve the surface quality and obtain a dense surface. The tungsten samples with a relative density of 98.31% were obtained with optimized parameter combinations: a laser power of 300 W, scanning speed of 400 mm/s, and hatch spacing of 0.08 mm. Compared with scanning speed and hatch spacing, the laser power had a more obvious influence on the relative density. Additionally, for the grain morphology by microstructure inspection, elongated curved grains gradually transformed into fine straight columnar grains as the scanning speed increased. The hatch spacing would change the grain morphology slightly but had no significant effect on the grain size.

Laser Powder Bed Fusion of Unalloyed Tungsten: A Review of Process, Structure, and Properties Relationships

“…Wang et al [34] have also reported a reduction in lack of fusion porosity when using spherical powder instead of irregular powder under same process parameters (Figure 4). Relative densities of unalloyed tungsten above 98% have been recently achieved by LPBF of spherical powder feedstock [36][37][38][39][40][41][42][43][44][45]. The research on RF plasma spheroidization of tungsten powder has also revealed favorable effect on powder particle size as reported by Zi et al [32] and Wang et al [31].…”

“…The result is immediate and seamless grain growth across the solidliquid interface [40,49]. A number of publications have also reported successful LPBF of tungsten (W) on compositionally different substrates such as steel [33,38,42,53,54] and titanium [48]. The presence of compositional difference between the liquid and solid phases in such cases is expected to impose a nucleation energy barrier and hinder the spread of molten metal on the substrate, leading to insufficient wetting.…”

“…Li et al [42] investigated the influence of process parameters such as laser power P, scanning speed v, and hatch spacing h on the density of as-LPBF bulk tungsten (W) parts and achieved maximum relative density of 98.31%. Densities were calculated using the Archimedes method and process maps were produced in the study (Figure 10).…”

Fabrication of Ultra-Fine-Grained W-TiC Alloys by a Simple Ball-Milling and Hydrogen Reduction Method

“…Tungsten and its alloys have been used for many engineering applications such as in the aerospace, automotive, nuclear energy, materials processing, and defense industries. They are also considered attractive materials for high-temperature applications such as heating elements, rocket nozzles, heat shields, and combustion chambers [ 1 , 2 , 3 ]. This is due to the superior properties of tungsten such as high melting point (3420 °C), high thermal conductivity, high tensile strength, and high hardness [ 1 , 2 , 3 , 4 , 5 ].…”

“…They are also considered attractive materials for high-temperature applications such as heating elements, rocket nozzles, heat shields, and combustion chambers [ 1 , 2 , 3 ]. This is due to the superior properties of tungsten such as high melting point (3420 °C), high thermal conductivity, high tensile strength, and high hardness [ 1 , 2 , 3 , 4 , 5 ]. In addition, due to its excellent radiation shielding properties, tungsten is also considered a promising plasma-facing material for future nuclear fusion reactors [ 5 , 6 , 7 ].…”