Materials used to make components for the next generation of lighter and
higher performing jet engines will include a
new, less-expensive superalloy.
ATI 718Plus alloy is the first
nickel-based superalloy to be used for both static and rotating jet engine
components in more than 40 years, according to Allegheny Technologies Inc. of
Pittsburgh. It's going into commercial production this year.
The superalloy is described as a workable, formable replacement material
for engine structures such as turbine cases, blades and shafts. Fasteners are
also potential applications. Heat treatment consists of solution treating
followed by a double aging treatment. Different heat treatments are used
depending on the mechanical properties desired.
The material can be welded in both the solution-treated and fully aged
conditions using inert gas-shielded arc, plasma arc, electron beam and
"ATI 718Plus alloy plays an important role in helping engine
manufacturers meet their aggressive goals for fuel efficiency and emissions
while providing as much as a 25-percent reduction in part cost over more
expensive nickel-based superalloys," says Rich Jeniski, director, marketing and
business development at ATI Allvac.
ATI says ATI 718Plus alloy provides a major performance advantage
over standard alloy 718: a higher operating range that will function reliably
at temperatures 100F hotter. Its cost advantage derives both from lower raw
materials' costs as well as improved manufacturability.
New jet engines are more efficient because of higher operating
temperatures. The hot gas path can be increased from 1200F to 1300F, requiring
higher-performing components. Emissions are also reduced because the combustion
cycle is more complete.
Another alloy used in the new jet engines is a gamma titanium aluminide
material supplied by ATI Wah Chang. It's used in the low-pressure section of
the GEnx engine that will power the Boeing 787 Dreamliner. It is said to have
half the weight of nickel-based alloys, but is able to withstand higher
operating temperatures, further extending fuel efficiency.
It's not specifically known if ATI 718Plus is used in engines designed
for the 787 Dreamliner. However, Rolls-Royce, one of the Dreamliner engine
suppliers, extensively tested ATI 718Plus at Rolls Royce Deutschland, which
established an evaluation and optimization program for the alloy. The program
included the development of a complete processing route as well as substantial
Allvac 718Plus alloy is available in mill product forms for end-use
applications that also include forging and extrusion dies.