Failure analysis of ring die of a feed pellet machine

Abstract

The severely worn position and failure mechanisms of the ring die of a feed pellet machine were investigated. The macroscopic and microscopic morphologies of the failed surface, the chemical composition and mechanical properties of the collected samples were analyzed using scanning electron microscopy, energy disperse spectroscopy, optical emission spectrometry, and a universal testing machine. Results show that the dip angle at the entrance of the ring die hole between the roller and ring die was severely worn. The feed powder could not be fully extruded through the dip angle at the entrance of the ring die holes, thus the density of the feed particles produced could not meet the requirements. Therefore, abrasive wear under high stress is the main reason of failure at the entrance of the ring die holes under the action of feeding powder; and cutting and fatigue spalling lead to substantial material loss. In addition, a high damp-heat environment aggravates abrasive wear on the die hole internal surface.

Keywords

• ring die; failure analysis; micro-cutting wear; fatigue-exfoliative wear; electrochemical corrosion