Stationary Shoulder Friction Stir Channelling: A leaner method of manufacturing heat exchangers for aerospace

Friction Stir Channeling (FSC) is an innovative solid-state process for the production of sub-surface networks in metallic components. One of the most promising industrial applications is the manufacture of heat exchangers. Other potential uses include the production of channels to embed instrumentation, wiring or mechanisms, as well as, lubrication networks or hydraulics. Additionally, FSC may also be used as a weight-reduction technique by fabricating hollow panels or structures. The first studies reported in the literature focused on using an approach similar to that of Friction Stir Welding (FSW), i.e. deliberately promoting poor material consolidation conditions and produce a continuous void along the tool path.

The present investigation demonstrates the feasibility of a newly patented technology variant called Shoulder Friction Stir Channeling (SSFSC). This technology was tested by processing AA6082-T6 and AA1050-H14 plates with a thickness of 15 and 20mm, respectively. The effect of the main processing parameters and tool geometry on channel cross section, microstructure and inner surface roughness was explored. SSFSC proved to be effective at controlling the channel cross-sectional consistency and a vastly improved as-processed surface finish. The area of the channels obtained varied between 5-40mm². Flat and tubular heat exchanger demonstrators were successfully manufactured, featuring channels along linear, curved and helicoidal trajectories. Heat exchanger performance criteria were also tested namely leak testing, burst pressure, heat transfer and fluid flow pressure loss.

Examples of potential aerospace applications are proposed, namely for engine thermal management, heat dissipation systems for hydraulics, anti-icing on wings and replacement of hot pipes.