Direction of R&D and Current Status of Understanding of Advanced Gear Steels

Abstract : High performance gears in the modern helicopter must operate at ever increasing torque and RPM. A major consequence of this increased torque and RPM is a significant increase in the surface temperature and increased scuffing of the gears. In response to this problem, Boeing-Vertol introduced a new class of steel (hot work tool steel) as a high performance aircraft gear steel and started a trend which all subsequent work has confirmed to be a correct decision. This report focuses on the three most prominent candidate critical high temperature aircraft gear steels including Vasco X-2M, CARTECH X-53 (PYROWEAR 53), and CBS600. The heat treatment responses of these alloys will be compared. Three additional alloys (M50NiL, CBS1000M, and AMAX b) will be discussed in less detail. Most of the information contained in this report is metallurgical in nature with the appreciation that considerable engineering and manufacturing information is available for most of the alloys, but with the realization that much work still needs to be done.