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Influence of Cobalt in the Tensile Properties of ½ Inch Ductile Iron Y-blocks

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Abstract

The ferrous industry keeps evolving, and the demand for castings with complex geometries is increasing. Due to this, some foundries are facing several challenges when it comes to producing highly complex parts with a specific microstructure. Normally, heat treatment is performed when a ferritic matrix is desired. However, distortion and cracking can become a problem too. Because of this, it is important to explore alternative methods that can potentially help with these problems. In ductile iron, cobalt additions are known to increase the nodule count, which favors higher ferrite fractions. Hence, the addition of cobalt was studied to investigate its effects on the microstructure and tensile properties of ductile iron. Five heats were produced and cast into ½ inch ASTM A536 Y-blocks: 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt% Co. Metallography was performed to evaluate the percent nodularity, nodule count (N/mm2), and ferrite/pearlite percentages. Tensile testing was executed using sub-size round samples. Brinell hardness and micro-Vickers were conducted on each Y-block to assess the macro and microscopic behavior of the cobalt bearing ductile iron. The addition of 4 wt% Co was found to decrease the nodule size and increase the percent nodularity and nodule count resulting in higher ferrite contents. Cobalt did not have a statistically significant effect in tensile strength and percent elongation. However, cobalt was found to increase the yield strength due to the solid solution strengthening effect in ferrite.

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Acknowledgements

Funding for the present work was provided by the Ductile Iron Society and the Materials Science & Engineering (MSE) department of Michigan Technological University. The authors acknowledge the Institute of Materials Processing and the MSE department for the use of processing equipment, characterization instruments, and staff assistance. Chemical analysis of all heats was performed by Neenah Foundry and Aarrowcast, Inc to confirm the chemical composition. Metallography for all heats was performed by Waupaca and Neenah Foundry to confirm the analysis done at Michigan Technological University. Technical assistance was offered throughout the project by Vadim Pikhovich who performed the simulation of the mold using Magma Software. Catherine Hartung, Lizeth Medina, Lyle Heberling, and Mathew Meyer who provided technical support at different stages of the project.

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  1. Michigan Technological University, Houghton, MI, USA

    Alejandra Almanza, Dale Dewald, Joseph Licavoli & Paul G. Sanders

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  1. Alejandra Almanza
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  2. Dale Dewald
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Almanza, A., Dewald, D., Licavoli, J. et al. Influence of Cobalt in the Tensile Properties of ½ Inch Ductile Iron Y-blocks. Inter Metalcast 15, 433–446 (2021). https://doi.org/10.1007/s40962-020-00521-3

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