Failure Analysis of a Pellet-Mill Die


One of the most important parts for pellet-mills is the die, since the die transforms raw materials in small cylinders called pellets. In this paper, a failure analysis was conducted for a pellet-mill die that had not reached its service life expectancy. The failure analysis consist of a characterization of the material using atomic emission spectroscopy, hardness measurements, optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy by SEM. Additionally, visual inspection and fractography of the fracture surfaces and FE analysis were performed. It was found that the die material was a CA40 alloy, which microstructure consists of a martensitic matrix with finely dispersed carbides of the type M23C6. Also, a non-common level of inclusion type Al2O3 was found on the microstructure of the die material. According to the fractographic analysis, the crack initiation was located in a high-stress concentration region on the counterbored holes of the die, and also aided by the inclusions on the structure. Crack propagated along the material as an intergranular brittle fracture.


Materials Science and Engineering

Keywords and Phrases

Failure analysis; Fractography; Martensitic stainless steels; Metallographic examination; Pellet-mill

International Standard Serial Number (ISSN)

1547-7029; 1864-1245

Document Type

Article - Journal

Document Version


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Publication Date

01 Apr 2016