A Novel Method for Microstructural Characterization of Gray Cast Iron
The difficulty in the metallography of gray cast iron lies in the differentiation of ferrite and iron phosphide eutectic (steadite) microconstituents using normal etchants like nital and picral, and both phases appear bright (white color, unaffected) under normal light microscopy. Hence, it is difficult to find out the relative amounts of phases either photomicrographically or using sophisticated image analysis software. On the whole, the samples are etched with 2–3% nital for quantification of ferrite, steadite, pearlite, and carbides under optical (light) microscopy. This method of inspection requires high skill to differentiate the ferrite and steadite microconstituents, and also, sometimes it leads to misinterpretation which results in uncertainty in results. This led to the development of a novel etching method using “selenic reagent” which unveiled different microconstituents in the microstructure with higher confidence level.
KeywordsCast iron Microstructure Quantitative metallography
The author would like to thank WABCO-TVS, Chennai, and Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras for their material and instrumental support, respectively.
- 1.RM Nunes: ASM handbook casting, 9th ed, Metals HandbookGoogle Scholar
- 2.J.P. Arul Mozhi Varman, Microstructural characterization of grey iron, in AIST Annual Meeting, p. 2183–2187 (2013)Google Scholar
- 4.W.A. Blower, Pattern design for high pressure molding. Trans. AFS 78, 313–316 (1980)Google Scholar
- 5.J.R. Davis, Cast Irons, ASM Specialty Handbook (ASM International, Materials Park, 1996)Google Scholar
- 7.J.P. Radzikowsk, ASM Handbook, Metallography and Microstructures (ASM International, Materials Park, 2004)Google Scholar
- 8.P.C. Rosenthal, R.W. Heine, C.R. Loper, Principles of Metal Casting, 2nd edn. (McGraw-Hill, New York City, 1967)Google Scholar
- 10.G. Petzow, Metallographic Etching: Metallographic and Ceramographic Methods for Revealing Microstructure, 1st edn. (American Society for Metals, 1978)Google Scholar
- 11.H.I. Sanderow, T. Murphy, Quantitative image analysis technique for determining local density variation. Adv. Powder. Metall. Part. Mater. 4(10/13), 13–111 (2000)Google Scholar
- 12.W. Conshohocken, Standard Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Anlysis, E1245-03 (ASTM Standard, Philadelphia, 1995)Google Scholar
- 13.W. Conshohocken, Standard Test Method for Determining Volume Fraction by Systematic Manual Point. E562-98, vol. 3 (ASTM Standard, Philadelphia, 2000)Google Scholar
- 14.Measurement of microstructure. https://mme.iitm.ac.in/vsarma/mm3320/Measurement%20of%20Microstructure.pdf. Assessed 23 June 2017