J. F. Lane, Applied Technical Services, Inc., Marietta, GA
Powder metallurgy gears are used in a variety of applications. Their ease of fabrication affords an economical process for producing high-volume parts. However, depending on the degree of consolidation, the structure and applied loading must be carefully controlled to prevent deleterious conditions from arising.
This presentation will discuss such a case. A manufacturer of small motors began experiencing a high rate of failure in the P/M drive gears. These failures were delayed, occurring during in-coming inspection, during assembly, during installation and even after being introduced in the field.
The cause of failure was identified as stress-corrosion cracking attributed to overstressing of the component by a steel pin inserted in the end of the gear and deleterious microstructural constituents in the nickel-steel parts.
P/M gears used in small motors were experiencing delayed failures. The failures were observed during in-comming inspection, assembly, installation and in the field. The failures were attributed to high residual stresses associated with a steel pin inserted in the end of the gear and environmental factors associated with the microstructure.
