October_2021_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 2 1 2 1 portional to temperature, and growth kinetics, which is proportional to tem- perature. In summary, the carbide forming elements were balanced to en- sure high nucleation driving force with tailored growth kinetics to yield a car- bide dispersion within a feasible man- ufacturing process in both the core and case. In the end, the ICME-enabled de- sign process yielded a novel alloy composition and process to achieve ag- gressive property targets by identifying and predicting the role of each element in the material microstructure [4,5] . COMMERCIAL DEBUT OF C64 A critical factor in the qualification and commercialization of C64 steel was establishing strong partnerships across the entire supply chain from the earliest development stages. These included: • Specialty steel producer and current licensee Carpenter Technology • Forgers such as Scot, ATI Ladish, and Larson • Heat treater Solar Atmospheres • Machining vendors Forest City Gear, Delta Gear, Triumph Group, and many others • Superfinisher REM Chemical In addition, a significant amount of fatigue data was developed at the Gear Research Institute and NASA Glenn Research Center. RIGOROUS QUALIFICATION PROCESS To facilitate end-user adoption, Ferrium C64 underwent the rigorous SAE Aerospace Materials Specification qualification process (designated as AMS 6509) for developing S-Basis min- imum design allowables. Compared to former best-in-class gear steels such as AISI 9310 (AMS 6265) or Alloy X53 (AMS 6308), the C64 data showed a tar- geted step-change in combination of strength, toughness, and surface hard- ness. Reports from industry are that C64 allows for ~20% increase in power den- sity or a ~20% reduction in component weight at the same power. Wrought Ferrium C64 steel has been supplied to many industries ranging from aerospace, oil and gas, and high-per- formance racing to hand tools and agriculture. Mil- itary applications to date are in partnership with the major U.S. helicopter OEMs for Future Attack Reconnaissance Aircraft (FARA) and Joint Multi- Role (JMR) Future Vertical Lift programs. IMPROVED MILITARY AIRCRAFT SAFETY Under the U.S. Army- funded Future Advanced Rotorcraft Drive System (FARDS) program, Bell Helicopter evaluat- ed Ferrium C64 steel for next-gener- ation helicopter transmission com- ponents. A main rotor gearbox was manufactured using Ferrium C64 steel along with several other novel technol- ogies. This demonstration gearbox was operated under a loss-of-lubrication test condition, which survived >80 min- utes of operation without failure in the C64 components. This result is illustrat- ed by post-test images of the gear shaft and input pinion in Fig. 2, showing only minor scuffing on the gear teeth and no failures. Existing best performing heli- copter gearboxes last <25 minutes due to the limited temperature stability of strengthening carbides in typical gear steels [6] . The high temperature stability designed into Ferrium C64’s strength- ening carbides enables it to perform at the elevated temperature of a gearbox oil-out condition where other steels fail. ADDITIVE MANUFACTURING PROGRESS QuesTek is actively transitioning Ferrium C64 into laser powder bed fu- sion additive manufacturing processes. Initial success based on multiple indus- trial scale atomization runs and print- ing on EOS M 290 equipment has shown equivalent static mechanical properties versus wrought C64 bar. Initial axial fa- tigue and single tooth bending fatigue results are also promising. C64 is already one of the most de- veloped high-performance steels for high hardness applications in additive manufacturing, and a new multi-year project is underway for it to be fully “additive ready” by 2023. Addition- ally, powder blown directed ener- gy deposition and binder jet AM trials are planned. C64 powder and print FerriumC64 steel FZG type test gear chemically processed by REM Chemical in as-ground (top of image) and after isotropic superfinishing (bottom). REM can achieve Ra ranges in 1-6 µin for C64. Courtesy of REM. Fig. 2 — FerriumC64 input shaft (top) and gearshaft (bottom) imaged after 85 minutes of loss-of-lubrication testing in Bell Helicopter’s Future Advanced Rotorcraft Drive System program. Results showminor scuffing on the gear teeth but no signs of surface damage or failure. Courtesy of Bell.