Optimization of case-hardening depth for small gears

Abstract: The optimization of case hardening depth for small gears was investigated with the use of Abaqus and the subroutine DANTE to simulate the formation of the microstructural phases, resulting in residual stresses and increased hardness. This was done with a step wise increment of the carburizing time, resulting in a theoretical maximum for compressive residual stresses at the surface. The heat treatment parameters were then used for case hardening two gears with different carburizing times. The heat treated gears were then tested for tooth root bending fatigue. The fatigue testing resulted in a fatigue limit increase, where the gear with largest simulated compressive stress showed the highest fatigue limit.   Both the heat treated gears were hardness tested and compared with the conducted simulations resulting in an underestimated hardness. An investigation to see whenever the simulations could predict the fatigue outcome beforehand with a probabilistic model was put into place. This resulted in an underestimated fatigue limit in relation to the raw fatigue data.