Aerospace & Defense Technology - October 2022 - 16

Optimized Cutting Tools
for Tomorrow's
Sustainable
Aircraft
" G
ood design is, for people and the planet, an increasingly
critical focus, " according to the UK Government's
UK Innovation Strategy. That includes
in aerospace, where tomorrow's aircraft will be
required to fly more sustainably and support net zero objectives
around the world. Optimized cutting tools and process
knowledge will be crucial to sustainability and innovation in
aerospace, especially when working with increasingly difficult-to-machine
materials.
Tomorrow's sustainable aircraft will rely more on next
generation powder-based heat resistant super alloys (HRSAs)
and advanced ceramic matrix composites (CMCs), as they
can withstand high temperatures for more efficient fuel burn
and low emissions. However, these materials are required
to be heat resistant and maintain their material properties
under extreme temperatures. This presents challenges at the
machining stage.
The UK Innovation Strategy report says that new technologies
and processes will be key to manufacturing and
machining these advanced materials at scale. Collaboration
within the industry will also be essential. For aerospace, if
we're talking about sustainability, then new technologies
and processes should focus on the ability to combust new
fuel types, like sustainable aircraft fuel and liquid hydrogen,
to create lower emissions.
As always, the ability to run hotter means there is a more
efficient fuel burn. If we couple this with higher compres16
sion
ratios, which most new and future engines can support,
then the result is greater efficiency. That means less fuel is
combusted with increased power and reduced noise.
Material Properties and Engine Components
With aero engines, the core of the engine is relatively
small and the fan on the front is relatively large. So, a
limiting factor is how fast you can rotate the fan. To remedy
this, over the last five to ten years, gearboxes have
been introduced between the fan and the core of the
engine. They enable the fan to run more slowly while the
engine core runs faster for high compression and better
fuel efficiency.
However, HRSA components are needed to make this
work. Such materials are metallurgically composed to retain
their properties when exposed to extreme temperatures. But
this also means the stresses generated when machining these
materials are high. The unique capability of these nickel,
iron and cobalt-based super alloys to perform close to their
melting point also gives them generally poor machinability.
HRSAs are so difficult to machine because they resist heat,
and the process used to machine them generates heat. When
shops machine a piece of steel, the chips that come off
absorb heat from the machining process. That is why steel
chips turn blue. In HRSAs, the chips resist rather than absorb
the heat, sending it back into tools or the workpiece. The
generated heat can turn the carbide of the cutting tool into a
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Aerospace & Defense Technology, October 2022
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Aerospace & Defense Technology - October 2022

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