Articles 

Improper Gear Meshing Leads to Premature Failure

2011-02-23

Several factors affect the performance and life of gears in the field. These factors can be broken down into categories which include geometry, metallurgy and installation/maintenance. With regard to geometry, one factor that influences the life is the tooth width1. Others include the number of teeth, diameter, face width and tooth thickness. Some factors which affect the performance from a metallurgical view include the case depth, surface hardness and microstructure. Case depths typically range from 0.005” to 0.040” and even deeper for certain applications. Typical surface hardness for case hardened gears ranges from the upper 50s HRC or low 60s HRC. Careful attention must be taken when manufacturing gears which are nitrided due to the possible occurrence of a very brittle surface commonly referred to as a white layer. Improper installation/maintenance is reported to be the greatest cause of gear failures as documented in Table 1 for a variety of reasons2.