Advances And Applications Of Pyrowear 53 In Helicopter Transmission Systems

The objective of this program was to identify the specific failure characteristics of the M-50 planetary bearing inner race, eliminate the problem by design or material change and qualify, by test, the final configuration for production incorporation. The failure characteristics of the bearing inner race were found to be primarily associated with the carbide morphology of M-50 material combined with the low EHD film thickness inherent in final stage planetary systems used in helicopter transmissions. Case carburizeable materials, such as the classical 9310 and the advanced High Hot Hardness Pyrowear 53, were selected to eliminate the carbide distribution condition. Additionally, the reported surface fatigue life superiority of Pyrowear 53 as a gear material recommended its evaluation as a bearing material. The conclusions drawn from the qualification test results show that both the 9310 and the Pyrowear 53 were successful. Moreover, the surface wear and degradation resistance of the Pyrowear 53 were slightly superior to those of the 9310.