Micro-CT Quantitative Evaluation of Graphite Nodules in SGI

• Published in: International journal of metalcasting Vol. 14; no. 2; pp. 318 - 327
• Main Authors: Lekakh, Simon N., Zhang, Xueliang, Tucker, Wesley, Lee, Hyoung K., Selly, Tara, Schiffbauer, James D.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-04-2020
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Materials Science; Metallic Materials; Structural Materials; spheroidal graphite; cast iron; solidification; structure; micro-CT scanning
• ISSN: 1939-5981; 2163-3193
• DOI: 10.1007/s40962-019-00354-9

The quality of spheroidal graphite cast iron (SGI) castings is directly related to the morphology of graphite nodules. Therefore, accurate and comprehensive quantitative evaluation of microstructure is critical for industrial practices. The most influential morphological characteristics of the graphite phase in SGI can be divided into three categories: (1) shape and size of individual graphite nodules, (2) total volume of graphite phase and nodule number, and (3) spatial distribution. During the last decades, SGI structure analysis has progressed from visual observation of polished cross section and quantitative 2D techniques (metallography and automated SEM/EDX) to observation of the real 3D structure using micro-computed tomography (µCT) scanning. In this article, 2D and 3D morphological characteristics of graphite nodules were determined by µCT scanning and compared. 3D µCT provides accurate characterization of the real shape factor and diameter of graphite nodules. It was shown that large and small graphite nodules in inoculated SGI have the different modes of space distribution which could be linked to casting solidification.