 |
 |
 |
 |
 |
|
 |
|
 |
Alloys are developed by the addition of minute amounts of elements (we're talking little - 0.001-0.035% by weight) during the metal's processing. The exact elements used depends upon the characteristic of the starting metal, but can include carbon, boron, sulfur, lead, zirconium, and phosphorous, among many others. These additives are made to improve the metal's physical and mechanical properties - formability, durability, strength, and lifespan.
 |
| Photo courtesy of ASM |
| Alloy 718 is used extensively in aircraft engines for compressor and turbine disks, cases, compressor blades, and fasteners. Shown is a GE 90-92B engine on the factory crane receiving final adjustments. These engines power the new Boeing 777. |
In aircraft engines, a nickel-based alloy called Alloy 718 is used extensively for compressor and turbine parts. First developed over 30 years ago by Inco Alloys International, materials scientists have made improvements through modifications to the chemical composition and processing techniques. For example, they have discovered that the addition of magnesium improves hot ductility, and using triple melting techniques (vacuum induction, electroslag, vacuum-arc) improved material cleanliness.
This improvement process is not static, either. In the case of Alloy 718, it was thought that the addition of phosphorous was detrimental, and was controlled to limit its inclusion. Recent studies performed by Teledyne Allvac have shown that controlled addition of phosphorous, carbon, and boron yields a significant improvement in stress-rupture properties.
To read more about this study, look at Advanced Materials and Processes, Volume 149, No. 3, March 1996, p. 33-34.
Site related questions or comments? Contact crc@tms.org