Ferrium® C61™ and C64™ are new secondary-hardening steels that provide superior mechanical properties versus 9310, 8620, Pyrowear® Alloy 53 and other steels typically used for power transmission, such as significantly higher core tensile strength, fracture toughness, fatigue strength and thermal stability (i.e. tempering temperature). One recent example of their application is the 2010 Small Business Innovation Research (SBIR) Phase IIAwardQuesTek received from the U.S. Army to demonstrate the application ofC61 to the forward rotor shaft ofCH-47 Chinook helicopter (working in conjunction with The Boeing Corporation), in order to reduce the weight of the shaft by 15-25% and provide other benefits.

This paper will review the significant manufacturing and processing benefits that arise from this new class of secondary-hardening steels, and analyze the potential implications and opportunities. C61 and C64 were computationally designed to take advantage of high-temperature, low-pressure (i.e. vacuum) carburization technology, in part by combining carburizing and austenitizing steps as well as being designed to have very high hardenability. The very high hardenability of these steels permits a mild gas quench subsequent to low-pressure vacuum carburizing and reduces part distortion, thus reducing grind stock removal, simplifying final machining and heat treat operations. A framework analysis will be used to compare total manufacturing/production costs and impacts (including environmental) of these new steels versus traditional gear steels. Conclusions and recommendations will be drawn regarding best manufacturing practices and appropriate use of these new steels for product applications.