ADVANCED MATERIALS
Alloys for Industry

Computer models of arc welding have been built at ORNL.

Material synthesis. The first ORNL-developed alloy to be commercialized was Hastelloy-N, first sold by International Nickel Company and now marketed by Haynes International. This nickel-molybdenum-copper-iron alloy was developed by Hank Inouye and others to contain the fuel used in the ORNL-developed molten-salt reactor. The alloy resists aging, embrittlement, and corrosion from exposure to hot fluoride salts.

Another commercialized alloy, modified chrome-moly steel, was developed by ORNL's Vinod Sikka and others in collaboration with Combustion Engineering for the nation's breeder reactor program. For 20 years the alloy has been produced by companies in France, Germany, Japan, and the United States for a total of more than $400 million in sales.

This alloy, which has excellent high-temperature mechanical properties, doesn't easily corrode or deform under normal operating conditions. Made mostly of iron, it is 9% by weight chromium and 1% by weight molybdenum, with a few trace elements added. It is used in utility boilers that produce electricity and in oil refinery furnaces that make unleaded gasoline.

Another alloy developed for the breeder project was an austenitic stainless steel that does not swell and become embrittled when exposed to high temperatures and fast neutrons (as explained by ORNL's Jim Weir). Jim Stiegler, Everett Bloom, and Arthur Rowcliffe developed a low-swelling stainless-steel alloy by doping it with silicon and titanium, using microstructural control technology. The alloy has been used for fuel cladding in breeder reactors in Japan and France.

ORNL's C. T. Liu and others developed modified nickel aluminide alloys that are now used to replace Bethlehem Steel's steel rolls (for moving steel plates into a furnace) and to make trays for Delphi Automotive Systems for heating and hardening surfaces of automotive ball bearings, gears, and valves.

Welding. ORNL, which has an international reputation in materials joining, has produced computer models that have helped U.S. industry solve problems in welding stainless-steel and nickel-aluminide alloys. ORNL researchers developed a test to evaluate weld-cracking susceptibility and brazing techniques that have been used nationwide. Laboratory models are guiding industrial welding repairs of nickel-based-superalloy, single-crystal turbine blades to be used in power-producing, land-based gas turbines. To help secure sensitive nuclear technologies, researchers led by Stan David and John Vitek are working with former weapons researchers in the Ukraine to develop repair-welding techniques for turbine engine components.

Material characterization. The design of low-swelling stainless steels at ORNL was enabled by parallel developments in analytical electron microscopy and transmission electron microscopy. AEM and TEM, as well as the three-dimensional atom-probe-field ion microscopy refined and used at ORNL, made possible a thorough understanding of microstructure and the composition of microscopic precipitates that form in steel during its manufacture. ORNL metallurgists changed steel composition to engineer its microstructure and obtain desired properties.

Since the 1960s ORNL researchers have developed optics to significantly improve the brightness and intensity of X rays for analyzing materials structure. Cullie Sparks' graphite monochrometer crystals are used worldwide for X rays and neutrons. In the 1980s Sparks and Gene Ice invented an X-ray-focusing method using curved perfect crystals for studies at synchrotron sources. Their precision crystal-bending methods that focus 20 times more radiation than alternative optics are now used in the world's most sophisticated X-ray facilities. In 2001 Ice and Ben Larson developed an X-ray microscope that enables studies of crystal grain structure with submicron resolution in three dimensions.

Z-contrast imaging of crystals, developed at ORNL by Steve Pennycook and others in the 1990s, allows scientists to use a scanning transmission electron microscope to see columns of atoms in materials ranging from superconductors to automobile catalysts. This technique achieved the highest-resolution image of a crystal ever produced. It is now available on commercially produced microscopes and is used worldwide.

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