Laser Powder Bed Fusion of Unalloyed Tungsten

Researchers from the Department of Mechanical Engineering, McMaster University have recently published a paper describing laser powder bed fusion of unalloyed tungsten in the academic journal Metals.

Tungsten (W) in its unalloyed form is used as a structural component in a variety of applications, including fusion reactors, heat exchangers, rocket engines, blast furnaces, and munitions. The unique properties of unalloyed tungsten, including its exceptionally high melting temperature (≈3422◦ C), good thermal conductivity, and low coefficient of thermal expansion, are important for these applications.

Tungsten is also a dense metal with X-ray attenuation properties comparable to those of lead (Pb), making it useful as an electron target in X-ray tubes, a collimator in radiosurgery, an anti-scattering grid in CT scanners, and a radiation shield in nuclear applications.

Traditionally, tungsten parts are produced by solid-state sintering after the metal powder is extracted from its minerals by powder metallurgy techniques. The sintering process usually requires post-densification operations such as machining, hot isostatic pressing (HIP), or post-filtration to reduce the inherent porosity of the sintered part.

A recent trend in integrating unalloyed tungsten powders is the use of laser powder bed fusion (LPBF) because of its ability to use laser energy to completely melt them. Another advantage is that LPBF offers superior shape versatility compared to the compacted dies used in powder metallurgy.

The production of tungsten 3D parts by laser powder bed fusion is accomplished by melting the tungsten powder layer by layer. A certain thickness of powder is laid flat on a substrate (build platform) and then selectively laser melted along a predetermined path generated by computer software. After solidification, each consolidated layer serves as a new substrate for subsequent operations. This process will be repeated until the entire part is built.

This article presents recent advances in the selective laser melting of unalloyed tungsten by laser powder bed fusion LPBF technology, focusing on the influence of process parameters on the developed structure and properties. Successful implementation of LPBF technology as an alternative to conventional tungsten manufacturing techniques can significantly improve design flexibility, resulting in improved product performance and cost.

Expected research directions in the medical industry, aerospace, defense, and energy include the development of single-piece thrusters for space propulsion systems and single-piece high heat flux exchangers for nuclear reactors.

• < Prev
• Next >