Systematic investigations on the influence of case depth on the pitting and bending strength of case carburized gears

High power transmitting gears are nowadays nearly always case carburized and hardened. The value of case depth is one important parameter that has to be specified by the gear designer for the heat treatment process. On the one hand, the available gear load capacity can be reduced with a case depth that is too small. On the other hand, unfavorable influences on the material properties and possible increased distortion by hardening and increased requirements for grinding may result from a case depth that is too large. In times of modern and increasingly optimized gear manufacturing, there is a fundamental need for the gear designer to know how to determine an appropriate case depth for his actual gear application in order to guarantee the required load capacity and taking into consideration the different basic principles in the nature of contact and bending stresses that are most relevant for gear load capacity.