To increase predictable life of precision gears, requires a process which simultaneously produces the required geometry accuracy and surface finish, as well as the desired state of compressive residual stress at the part surface. The goal is to increase power throughput by optimizing the surface properties of the gears, without compromising tooth scoring resistance. In this experiment, four different surface enhancement processes were selected, implemented, and tested. Rolling Sliding Contact Fatigue tests were used to qualify the percentage of improvement. A set of test specimens were also made without any of the surface enhancements above. These specimens were used as the baseline for comparison.
9310 steel was used as the material to prepare the test specimens. All specimens were carburized, hardened and ground to the aerospace specification. Gear Research Institute conducted testing on all samples. The baseline specimens were all run in high-load, short-cycle tests and they failed in the predicted manner with expected scatter. The performance of some surface-enhanced specimens exceeded the performance of the baseline specimens. Improved life-to-failure rates were as high as 10%.
This paper will discuss the test specimen preparation processes, testing process and results of this project. It also includes recommendations for future work in surface enhancement.