PREDICTING CASE DEPTHS FOR GEARS.

When gears transmit torque, they are subjected to bending and contact loads which, when applied repeatedly, can cause the gears to fail by fatigue. This article outlines an analytical approach for predicting case depth requirements for carburized and hardened gears that can save as much as 30% of process time. Once the steel composition and quench rate are chosen, the best carburizing cycle is the one that develops a strength gradient such that fatigue strength will exceed applied stresses at all points on and below the surface with a reasonable level of safety.