The properties of gray iron are highly dependent on the size, shape and distribution of the graphite flakes. In spite of the importance of the graphite structure, quantitative analysis of the flakes has been underutilized in the foundry industry. In this study, methods for analyzing the characteristics of graphite flakes in gray iron are described. A metallographic sample preparation technique that works on a wide variety of irons and is not user specific was developed. This technique uses a dry grinding/etching process, followed by a polish with 1.0 micrometer diamond abrasive. Manual grid counts of the vol% of graphite were demonstrated. The results showed that, if insufficient measurements were made, the values obtained were not accurate. However, statistical analysis showed that, even with few measurements, the relative amounts of graphite between samples could be ranked. Automated image analysis (AIA) of graphite in gray iron was investigated, using both an optical and scanning electron microscope (SEM). The analysis indicated that consistent results are highly dependent upon duplicating the image input conditions and the discrimination procedures. Volume percent graphite and surface area of graphite-to-volume material measurements were successfully made, using an optical microscope with the AIA system. However, AIA flake length measurements required the use of SEM images to achieve sufficient resolution and contrast, without cutting off large flakes.
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