In situ running-in analysis of ground gears

• In situ surface measurements were used to measure surface changes and wear of gears.
• Surface transformation in gears is shown to occur at the initial cycles of operation.
• Friction curves during running-in show a rapid decrease and then a slight increase.
• Higher running-in load during running-in leads to a smoother surface.

The initial contact state between two interacting gears proves of interest due to empirical evidence indicating difference in life and efficiency in the long term due to the initial operation. Presented here is an analysis of the initial contact state of spur gears, made of case carburized 16MnCr5 steel, by the use of in situ surface measurements and friction measurements in a back-to-back test rig during the running-in cycles. Furthermore a method to estimate wear during running-in is proposed. Results show that the most significant changes in roughness and friction occurred during the first initial cycles at high load.