| Abstrakt: |
Three similarly-manufactured but differently-employed pellet mill dies of X46Cr13 (420C) stainless steel were broken into several parts. To determine the causes of fracture, material characteristics (such as microstructure) and features of crack faces were investigated. It is figured out that sensitization, which is the existence of continuous carbides on the prior-austenite grain boundaries, has taken place both in the dies and the as-received primary rings. In addition, studies on the crack faces reveal the occurrence of fatigue, corrosion, and intergranular fracture. It can be concluded that corroded sites of die 1 and sharp edges of dies 2 and 3 act as fatigue initiation spots, and final crack growth takes place mostly by intergranular fracture, owing to the presence of continuous carbides. The results show the importance of microstructure control for primary rings, design modification for the dies to reduce stress concentration, and cleanliness of the dies in non-operating periods. [ABSTRACT FROM AUTHOR] |
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