Articles 

Improper Forging 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 metallurgy, one factor that influences the life is the tooth width1. Others include the number of teeth, diameter, face width, and tooth thickness. Some factor, which affect the performance from a metallurgical view include the case depth, surface hardness and microstructure. One major factor which is commonly overlooked is the proper forging process to optimize the mechanical properties. Microstructural features attributed to the forging process should be oriented such that the major loading axis is not perpendicular to the direction of grain flow. This is critical at the root of the gear teeth where high tensile stresses are present. Improper installation/maintenance is reported to be the greatest cause of gear failures as documented in Table 1 for a variety of reasons2.