Next-generation multi-laser additive manufacturing of high-density tungsten for nuclear reactor shielding (working with UK Atomic Energy Authority)

Details

Project reference code: MEC-06-Mumtaz

We invite applications for an exciting four-year PhD opportunity, funded through an EPSRC DTP Studentship at the University of Sheffield and working in collaboration with the UK Atomic Energy Authority.

Laser powder bed fusion is an additive manufacturing technique that in recent years has seen a significant increase in industrial usage for the manufacture of high-value end-use components in the aerospace, automotive, energy and medical sectors. It is widely viewed as a disruptive alternative to conventional manufacturing processes, capable of creating geometrically efficient complex structures with low material wastage from a variety of high-performance metallic alloys (e.g. titanium, nickel alloys etc.).

Tungsten is an extremely dense material, it possesses high hardness and elastic modulus characteristics and the highest melt temperature among all metals. Within the nuclear sector, it is typically used as a plasma-facing component for first wall sections within a nuclear fusion reactor. Pure tungsten plasma-facing components with high geometric complexity (e.g. featuring complex cooling channels) are expected to improve fusion energy production efficiency as they could potentially operate at higher plasma temperatures. The processing of tungsten using laser powder bed fusion presents opportunities to enhance component performance through geometric optimisation. However, the material is challenging to process due to its high melt temperature and ductile to brittle transition temperature. The high thermal gradients generated by the fast-moving laser within laser powder bed fusion make the processing of tungsten challenging, creating high residual stresses within the material and defects such as cracks.

A new alternative to laser powder bed fusion has been developed at the University of Sheffield called Diode Area Melting. This multi-laser process uses a compact array of fibre-coupled blue diode lasers, with over a thousand lasers integrated into the laser head, selective melting of the feedstock can be undertaken with precise control over heat input. The process has been shown to significantly reduce the melt pool cooling rate and thermal gradients generated compared to traditional laser powder bed fusion, with the ability to control and customise microstructure.

This PhD project will use the novel Diode Area Melting technique to process tungsten powder with the aim of creating a high-density, crack-free structure suitable for plasma-facing components within nuclear reactors. Objectives include identifying suitable laser processing conditions to successfully heat tungsten above its 3,422°C melt temperature, characterisation of properties (e.g. part density, crack density, microstructure etc.), identifying thermal melting regimes (laser array activation within laser head) that prevent crack development through controlled melt pool solidification and creation of nuclear reactor components for benchmarking trials. This research project will help develop the underpinning science related to next-generation laser manufacturing technology and the processing of high-performance materials, paving the way for the creation of new products with enhanced capabilities.

 How to Apply

Applications should be made through the University of Sheffield on-line submission system and select code MEC-06-Mumtaz https://www.sheffield.ac.uk/arpform/login.app?code=EPSRC

 Interested candidates are strongly encouraged to contact the project supervisor (Professor Kamran Mumtaz, ([email protected]) to discuss your interest in and suitability for the project prior to submitting your application. 

 Please refer to the EPSRC DTP webpage for detailed information about the EPSRC DTP and how to apply.