Intermetallic Alloy Development A Program Evaluation (1997) / Chapter Skim
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2 OAK RIDGE NATIONAL LABORATORY INTERMETALLICS PROGRAM
2 OAK RIDGE NATIONAL LABORATORY INTERMETALLICS PROGRAM
Pages 10-31
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From page 10... ...
In response to the need for low density, high performance alloys for use in the components of airframes and turbine engines (NRC, 1993, 1996) , for example, concerted efforts have been made in recent years to improve the properties of intermetallic alloys, especially alloys based on aluminides (e.g., TiAl, Ti3Al, NiAl, Ni3Al, FeAl, 10
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From page 11... ...
In this chapter, the ORNL program for developing intermetallic alloy materials and processes is described; program management and interactions among the sponsoring groups within DOE are outlined; significant technical accomplishments and collaborations with industrial partners and licensees are reviewed; and conclusions and suggestions concerning the technical program are presented. The emphasis of this report is on lessons that can be derived from the development of Ni3A1 alloys and processes, which have been the focus of the OIT intermetallics research program at ORNL.
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From page 12... ...
The objective was to develop a new class of structural materials for advanced energy conversion systems by developing ductile intermetallics using microalloying processes. Thus, from the beginning, the purpose of this program was not just to investigate interesting questions of materials science, but also to identify and facilitate industrial applications for the new materials.
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From page 15... ...
Based on the Cummins license and the results of the workshop, efforts were made beginning in 1986 to support industrial applications focused on material processing technologies, including isothermal forging and rolling, near-net-shape casting and rolling, injection molding of powder into shapes, and extrusion, rolling, and forging. For the first three years, the alloy development efforts were primarily devoted to improving the durability and fabricability of wrought alloys.
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From page 16... ...
In the early 1980s, ORNL initiated a program to increase the understanding of the generally brittle behavior of intermetallic compounds and to modify that behavior by alloying and processing changes so that intermetallic alloys would be useful as structural (load bearing) materials.
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to Ni3A1 strongly ameliorated intermediate-temperature oxygen embrittlement, presumably by encouraging the formation of an impenetrable surface oxide layer (Liu and Sikka, 1986~. Following these discoveries, the Ni3A1 intermetallic alloys were strengthened using conventional alloying techniques to produce alloys with sufficient strength to be considered as replacements for currently used materials (e.g., Fe-Ni-Cr steel alloys)
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From page 18... ...
Additional testing is needed to provide engineering properties, like creep, fatigue behavior, and fracture toughness, that would enable expanded use of Ni3A1 alloys in more critical structural applications. Recent alloy development at ORNL (in the late 1980s and early 1990s)
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From page 19... ...
· IC-221 M IC-396 · HU ~ 10 ~1 ~ O- 1 1 1 1 1 p 0 200 19 FIGURE 2-4 Mechanical properties of cast Ni3A1 based alloys (IC-221M and IC-396M) and Fe-Ni-Cr steel alloy as a function of test temperature.
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From page 20... ...
, mechanical working, rolling, and welding. Although the ORNL investigations began as a development program for wrought alloys, the investigators shifted the emphasis of the program toward the development of casting alloys and processes in response to the desire by Cummins Engine Company, an early licensee, to produce cast components.
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Iron aluminide alloys are remarkably oxidation and sulfidation resistant and are therefore of great interest to the chemical and fossil fuel industries. The investigation of Fe3A1 materials and process technology has been part of the ORNL intermetallics program since 1988.
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The licensing strategy now being followed by ORNL has evolved since 1985. The first license agreement, signed in 1985 with Cummins Engine Company, was for the use of Ni3A1 alloys in diesel engine components.
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From page 23... ...
The improved oxidation resistance of the nickel aluminide alloys can reduce the incidence of surface blemishes introduced onto furnace rolls during service and thus improve the surface quality of the steel slabs being transported by the rolls. Another potential benefit could be to reduce the furnace down time required to maintain the rolls.
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Industrial welding capability for nickel aluminide alloys will enhance the commercial viability of furnace rolls and be important for many other applications.
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In comparison with the steel alloys now being used, nickel aluminides offer potential advantages of superior carburization and oxidation resistance, higher elevated temperature strength, and higher creep strength, which would reduce scheduled and unscheduled down time in heat-treating furnaces. If these advantages can be realized, an additional payoff could be savings in energy because assemblies produced with less mass require less energy to heat.
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From page 26... ...
Delphi believes there is a risk in the large-scale use of nickel aluminides in production carburizing furnaces because of an incomplete understanding of the models) of failure.
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Other Industrial Interactions ORNL identified a number of other industrial interactions related to Ni3A1 alloys that are under way. These include: · processing technology for sand and centrifugal castings (AECC)
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CONCLUSIONS This remainder of this chapter presents the panel' s evaluation of the progress and accomplishments of the ORNL program to develop intermetallic alloys. The evaluation includes conclusions pertaining to program management, the conduct of the technical program, and industrial interactions.
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From page 29... ...
Technical Program The ORNL intermetallic alloy development program has made significant technical advances since its inception from basic exploratory research and characterization through process development and scaling. The early decision to focus on Ni3A1 and to concentrate on optimizing alloy composition, characterizing material behavior, and developing production-scale processing methods has been critical to the success of the program.
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From page 30... ...
Although considerable progress has been made, significant work must still be done to enable Ni3A1 alloys to be used for commercial production, including: fundamental research to determine the mechanisms of ductility enhancement provided by alloying elements so that alloy composition can be further optimized characterization testing to provide engineering properties, for example creep, fatigue behavior, and fracture toughness development of data to model solidification (casting and welding) processes and to establish production processing standards and the development of methods for machining and welding nickel and iron aluminides REFERENCES Anton, D.L., D.M.
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From page 31... ...
1992. Alloy modification of gamma-base titanium aluminide for improved oxidation resistance, creep strength, and fracture toughness.
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