Open Competition 2 - Chemistry and Materials

Clean Metal Nucleated Casting of Superalloys

Sponsor: ATI Allvac (formerly Allvac)

• Project Performance Period: 11/1/2001 - 10/31/2006
• Total project (est.): $5,278,608.00
• Requested ATP funds: $2,596,466.00

Joint venture partners Allvac and the General Electric Company Corporate Research and Development (Niskayuna, N.Y.) propose to develop a fundamentally new, more efficient technology for producing advanced metal alloys for the power industry. High efficiency gas turbines used in electric power generation are among the most demanding applications for modern metallurgy. The failure of a large turbine disk, rotating at 3,600 rpm, can throw fragments weighing thousands of kilograms as far as a kilometer. The trend in turbines is toward more efficient designs, which means higher operating temperatures -- in excess of 600 degrees Celsius. To meet these extraordinary demands for strength and heat-tolerance, metallurgists have developed nickel-based "superalloys," but the complex chemistry of these alloys make them difficult -- and expensive -- to produce. Current casting technology for superalloys already has been pushed to the limits and cannot be scaled further to make the next generation of large ingots needed for new high-efficiency, higher-output turbines. Allvac and GE intend to develop a commercially practical version of a new technology, clean metal nucleated casting (CMNC) that could produce large, fine-grained, homogeneous superalloy ingots at a rate 6 to 10 times faster than the state of the art, and cut the number of melting steps needed to make a superalloy by a third. The fine-grained structure obtained directly from CMNC should make it possible to sharply reduce or eliminate the thermomechanical processing steps needed to convert the ingot into forgeable billets. The proposed technology would make possible larger, more complex alloy ingots than can be achieved by the present-day casting method. If successful, CMNC is expected to change the process for the casting of superalloys from one of liquid processing to one of casting in the semi-solid state, thereby enabling large gains in productivity, small grain size and compositional uniformity. To work, the liquid metal must be free of oxide contaminants that are commonly introduced by erosion of high-temperature ceramic components used in conventional casting. There are as yet no satisfactory non-ceramic replacements for these components, and developing one is considered the single biggest risk of the project. In addition, an experimental system to validate the process parameters will have to be developed, and models created to predict the scale-up to commercial dimensions. Finally, the exact processing steps needed to get from CMNC ingots to forgeable billets are not yet known. The partners approached the ATP because, although potentially revolutionary, commercial-scale CMNC is considered a long shot because of the R&D risks, the long time until payoff, and the sizeable investment required. Commercialization of the technology could contribute more than a $1 billion annually to the economy through the construction and sale of the new turbines it. Additionally, the technology is expected to enable entirely new superalloy materials.

For project information:

Howard Freese, (704) 289-4511
howard.freese@allvac.com

Active Project Participants

• GE Global Research Center (formerly GE Research) (Niskayuna, NY)
  [Original, Active Member]
  

ATP Project Manager

Jean-Louis Staudenmann, (301) 975-4866
jstaudenmann@nist.gov