Materials Needs and R&D Strategy for Future Military Aerospace Propulsion Systems (2011) / Chapter Skim
Currently Skimming:
Appendix E: Materials Development Case Studies
Appendix E: Materials Development Case Studies
Pages 188-197
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 188... ...
It is instructive to examine several of the advanced materials through the development process to identify how the successful materials and manufacturing processes produced propulsion advances or in some cases did not realize the expected potential of the material.
|
From page 189... ...
These are significant characteristics, as they make GE 48-2-2 attractive from an engineering and manufacturing standpoint. For comparison purposes, competing gamma TiAl alloys typically had nominal ductilities that were less than 1 percent and required environmental barrier coatings for extended use in the operational environment.
|
From page 190... ...
GE generated the first draft of the LPT blade design practice for a TiAl blade, including attachment considerations and key materials property requirements. An initial draft of a materials specification was also done.
|
From page 191... ...
Cost targets were met on a projected basis, but due to the unknown risk of achieving the cost-versus-weight benefit, plus immaturity of the supply chain with respect to meeting aggressive engine development program commitments, implementation was not pursued. 1997-2004 During the 1997-2004 time frame, only Japan's ESPR funding kept gamma TiAl research alive at GE.
|
From page 192... ...
E.1.2 Development of Gamma TiAl at Allison Gas Turbine A range of Air Force and Navy contracts supported titanium aluminides tech nology development at Allison Gas Turbine (now Rolls-Royce North America, Inc.) in the 1980s through the early 2000s, including the following: Hot Rolling of TiAl Sheet; Turbine AF applications; Composite Disk Validation; Gamma Ti Aluminides Development; High Temperature Coatings for Ti Aluminides; Join ing of Aluminides and Metal Matrix Composites; Damage Tolerant Design with Gamma; and Integrated High Performance Turbine Engine Technology (IHPTET)
|
From page 193... ...
Most of the development work and understanding of gamma TiAl led to the development of compressor blades and vanes, and these were successfully tested in both Advanced Turbine Engine Gas Generator/Joint Technology Demonstrator (ATEGG/JTDE) and CAESAR test engines, but have not yet found production applications.
|
From page 194... ...
A key environmental requirement associated with reusability is properties at elevated temperatures in air over extended periods of time. The results of these tests revealed that alpha-2's oxidation resistance over time was unsatisfactory and was actually no better than high-temperature titanium alloys such as Ti-6242 or Ti-834.
|
From page 195... ...
It failed to meet several of the key criteria associated with the applications at the time, and an alternate material was improved to the point that it became the prime candidate. Eventually, the major airframe systems pull disappeared altogether owing to the cancellation of the NASP Program.
|
From page 196... ...
; no other materials will work (it is the only material that will provide the required proper ties for the combustor and turbine -- the hottest and most demanding sections of a gas turbine engine) ; excellent adaptability/flexibility (an unparalleled ability to FIGURE E.2 Improvements in alloy temperature capability.
|
From page 197... ...
There are a variety of compatible alloying element chemistries, including aluminum, chromium, cobalt, iron, and tungsten. In the case of nickel superalloys, there has been a tremendous synergy between scientific understanding and applications -- scientific understanding of the relationships between microstructure and high-temperature properties, and applications that have benefited from this understanding in the form of improved materials and processes.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.