Ferrium® C61™

Ferrium C61 is a premium-quality steel that offers high fracture toughness, high fatigue strength, high core strength, high temperature resistance and high hardenability, and which can achieve surface (i.e. case) hardness up to 60-62 Rockwell “C” (HRC) via carburizing.  It was designed to permit use of low-pressure (vacuum) carburization technology with a direct low pressure gas quench. Applications can include armor plate, actuators, gears, driveshafts, and power transmission components where durability, compactness, weight savings, high temperature resistance or high surface fatigue resistance is valued. Its performance is race-proven, with more than 100 ring-and-pinion sets made of C61 used in highly demanding SCORE International® off-road races such as the BAJA 1000. C61 is covered by SAE AMS 6517.

Want even greater surface hardness?  See Ferrium C64.

Want even greater strength and can tolerate less surface hardness?  See Ferrium M54.

Benefits

Benefits of using C61 vs. alloys such as 9310 or 8620 for power transmission applications can include:

• Greater gear durability. Gears and gearboxes using C61 can handle higher impact loads and internal stress than comparable designs using traditional materials, or in some cases be reduced in size and weight, due in part to C61's very high fracture toughness and bending fatigue resistance. As one example, C61 ring-and-pinion sets used in SCORE International off-road racing have demonstrated a ~3-4x improvement in lifetime vs. identical parts made of 9310 (see below). 
• Smaller, lighter-weight driveshafts (or greater throughput). Integral driveshafts (e.g. with integral gears) using C61 can handle approximately 20-25% higher loads than comparable driveshafts using traditional materials, or be reduced in size and weight by comparable amounts. C61’s core UTS of 240 ksi is a ~39% increase vs. 9310, for example.  As one illustration, the weight of the main rotor shaft of a CH-47 helicopter can potentially be reduced by 15-25% without making significant changes to the production process (see below).
• Reduced manufacturing times and costs, with increased flexibility and control. C61 was designed to resist grain growth even at high temperatures, have high hardenability, and use vacuum carburizing with a direct low pressure gas quench, to thus: maintain good properties in large, thick-sectioned components (even with vacuum carburizing); reduce final machining/finishing costs by eliminating intergranular oxide formation and reducing quench distortion; eliminate the time, expense, equipment and non-uniformity of the traditional after-carburizing oil quench “hardening” step; and permit “dial-in” control of carburized case hardness profiles.

• Superior high temperature operability and survivability such as in oil-out emergency conditions or high-temperature environmments. The 900°F tempering temperature of C61 is 400-600°F higher than most incumbent alloys, yielding superior thermal stability and allowing gearboxes to run hotter (thus reducing cooling system weight, size, drag, etc.).

Licensed Supplier / C61 Price and Availability

As shown at left please directly contact our commercial production/sales licensee Latrobe Specialty Metals Company for C61 material pricing, availability and information.

Technical Assistance

If you have a specific application engineering or technical question that is not answered by our licensee's resources and the additional information below, then feel free to Contact Us.

Design and Development Background

In 2010 we began a U.S. Army-funded SBIR Phase II project to evaluate the use of C61 to replace 9310 as the material of construction for the forward rotor shaft of the Boeing-designed CH-47 Chinook helicopter.  It is expected that the weight of this large shaft can be reduced by 15-25%, and that total thermal processing and manufacturing operations can be simplified.

VW 091 Ring and Pinion Sets

To foster the commercial introduction and showcasing of C61, we've managed the production of more than 100 ring-and-pinion sets made of C61 for Volkswagen 091 transmissions used in 1600 class of the SCORE International off-road desert racing series, which demonstrated a ~3-4x increase in operating lifetime vs. parts made of 9310. Individuals seeking to obtain small numbers of VW 091 ring and pinion sets made of C61 material should contact Dave Folts Transmissions of Ontario, CA, USA at telephone #1-909-923-5970. If larger quantities are desired, please contact us directly.