  Turbine blades.
A turbine engine works by forcing hot combustion gases from the burning of fuel to flow through a series of fans, causing them to spin like a windmill in the wind. Except in this case the wind is a supersonic blast of burning hot gas and the windmill is spinning at 20,000+ RPM. To operate efficiently (and they are very efficient) turbine engines must run at high speeds and high temperatures, which means the stresses on the turbine blades are incredible. They have to be very strong,and more importantly they have to be very strong at very high temperatures. Nickel-based superalloys make this possible.
These particular turbine blades are old ones taken out of service. They were used in the famous "Huey" helicopters you've seen countless times in the movies. Analysis by x-ray fluorescence spectroscopy at the Center for Microanalysis of Materials, University of Illinois (partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439) indicates that they are mostly iron, 20% chromium, 4% nickel. I'm listing them under nickel because it's the nickel that gives them their special strength, though this analysis is at odds with their being nickel-based superalloy blades as represented by the source. However, XRF of metal surfaces can be misleading, and the measurement was not done very carefully, so I'm going to optimistically assume they are actually made of a superalloy.
Source: eBay seller getnick
Contributor: Theodore Gray
Acquired: 27 February, 2003
Text Updated: 16 March, 2009
Price: $30/10
Size: 2.5"
Purity: >50%
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