Abstract
The choice of alloying method for ferrous powder metallurgy alloys is often dictated by the oxidation potential of the alloying elements used in powder and compact manufacture. Silicon is effective in improving properties of ferrous PM steels; however, if added to the melt prior to atomization, the likelihood of oxidation is high. Alternatively, Si-rich and more complex particulates can be combined with the base powder, i.e., iron or low-alloy steel, with alloying occurring by solid-state diffusion during sintering. The effectiveness of these additives to improve material properties is dependent on their distribution throughout the material volume, as determined by diffusion of each added element. In this study, the distribution of silicon was quantified using energy-dispersive spectroscopy on an iron-based alloy composition. These data were compared with the volume fraction of the various transformation products in cross sections of hardenability samples using both light and electron microscopy. Predictions on the effects of local chemical composition, cooling rate, and microstructure are made.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
C. Schade, T. Murphy, A. Lawley, R. Doherty, The influence of silicon on the mechanical properties and hardenability of PM steels. Int. J. Powder Metall. 49(4), 9–20 (2013)
T. Murphy, B. Lindsley, C. Schade, A metallographic examination into fatigue-crack initiation and growth in ferrous PM materials. Int. J. Powder Metall. 49, 23–34 (2013)
B. Lindsley, H. Rutz, Effect of molybdenum content in PM steels, in Advances in Powder Metallurgy and Particulate Materials, vol. 7, ed. by A. Lawley, P. McGeehan, R. Lawcock (MPIF, Princeton, NJ, 2008), pp. 1–10
N. Bredzs, C.C. Tennenhouse, Metal-metal oxide-hydrogen atmosphere chart for brazing or bright metal processing. in Welding Research. Supplement to the Welding Journal, May 1970, (Wall Colmonoy Corporation, Detroit, MI, 1970), pp. 189s–193s
M.N. Gungor, A statistically significant experimental technique for investigating microsegregation in cast alloys. Met. Trans. A 20A, 2529–2533 (1989)
R.T. DeHoff, Application of stereology to the statistical description of the spatial distribution of composition and other scalar properties in three dimensional space. Acta Mater. 51, 2259–2269 (2003)
E.E. Underwood, Quantitative Stereology, 1st edn. (Addison-Wesley Publishing Co. Inc., Reading, MA, 1970), pp. 29–30
J.E. Hilliard, Measurement of volume in volume, in Quantitative Microscopy, ed. by R.T. DeHoff, F.N. Rhines (McGraw-Hill Book Co., New York, NY, 1968), pp. 45–76
Acknowledgments
The authors would like to thank Wing-Hong Chen for his assistance in making and testing the samples used in this study and Jerry Golin, Barry Diamond, and Eric Alesczyk for their assistance with the metallographic sample preparation and testing.
Author information
Authors and Affiliations
Corresponding author
Additional information
This article is an invited paper selected from presentations at “Fifty Years of Metallography and Materials Characterization,” a symposium celebrating the 50th Anniversary of the International Metallographic Society, held during MS&T’17, October 8-12, 2017, in Pittsburgh, Pa., and has been expanded from the original presentation.
Rights and permissions
About this article
Cite this article
Murphy, T.F., Schade, C.T., Lawley, A. et al. A Metallographic Study on the Diffusion Behavior and Microstructural Transformations in Silicon-Containing Powder Metallurgy Steels. Metallogr. Microstruct. Anal. 7, 650–660 (2018). https://doi.org/10.1007/s13632-018-0490-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13632-018-0490-x