#7FE. You asked for it and we have now provided it. As the enormous potential of the Cummings engine continues to be tapped so do the limits of the components that support it, specifically transmissions. Every aspect of of this new shaft and hub has been considered with excruciating detail paid to even the metallurgy of the material used. One of the biggest issues when creating a shaft like this is metal fatigue and shock loading. The requirements were that the material needed to be extremely stable and incredibly rigid. This shaft also needed to be able to withstand repeated shock loading with torque loads in excess of 2,700 ft lbs. That’s right 2,700 ft lbs of torque! The engineers knew of only one material at the top of there wish list, Aermet. That’s not a typo, this shaft is made from Aermet 100, as expensive as it was (raw material) this seemed to be the only logical solution. Here are a few metallurgy facts about AerMet alloy.
AerMet 100 Alloy Key features:
- AerMet alloy is an ultra-high strength type of martensitic alloy steel. The main alloying elements are cobalt and nickel, but chromium, molybdenum, and carbon are also added. Its exceptional properties are hardness, tensile strength, fracture toughness, and ductility. Aermet is weldable with no preheating needed. AerMet alloy is not corrosion resistant, so it must be sealed if used in a moist environment. AerMet is a registered trademark of Carpenter Technology Corporation.
- The UNS number is K92580. The alloy has a modulus of elasticity of 28,200 ksi and a density of 0.285 lbf/in3 (7.89 g/cm3). AerMet 100 alloy is somewhat more difficult to machine than 4340 at HRC 38. Therefore, carbide tools are usually used. Standard shapes that are available include round, sheet, welding wire, billet, plate, strip and wire.
- AerMet alloy is special in that it must be hardened twice in order to reach its maximum effectiveness. The first hardening application is a solution treatment at 1,625 °F (885 °C) for 1 hour. It is then quenched to a temperature of 150 °F (66 °C) over 1 to 2 hours. It then must be cold treated, where the material is cooled to −100 °F (−73 °C) for 1 hour. The second hardening process is aging, where the material is heated to 900 °F (482 °C) for 5 hours.
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