Fracture analysis of gear pump used for polymer production

In this study, the fracture of gears for polymer injection pumps fabricated via P/M (powder metallurgy) is investigated. In order to study the causes of the fractures, specimens prepared from the damaged gears were subjected to hardness, chemical analysis and metallurgical tests. The effect of microstructure on the fracture was also considered. Detailed metallurgical analysis was conducted on the fractured gears and compared with the unfailed gears in service. Results showed that gears hardness values were higher than values stated in the literature. Geometrical analysis of the gears revealed that early failure of the structure started from a sharp corner radius by which stress concentrations are created in the gear keyway.