Observation of Nanometric Silicon Oxide Bifilms in a Water-Atomized Hypereutectic Cast Iron Powder

This study investigated the reasons for the irregular structure of primary graphite nodules that were formed in a hypereutectic cast iron powder during water atomization. The graphite nodules contain a significant amount of micron-sized pores and multiple nanometric voids that formed from silicon ox...

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Bibliographic Details
Published in:Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2016-10, Vol.47 (5), p.2971-2978
Main Authors: Boisvert, Mathieu, Christopherson, Denis, L’Espérance, Gilles
Format: Article
Language:English
Subjects:
ATOMIZATION
Biofilms
CAST IRON
Casting
CASTINGS
Characterization and Evaluation of Materials
Chemistry and Materials Science
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTAL GROWTH
DEFECTS
EUTECTICS
GRAPHITE
Iron
MATERIALS SCIENCE
MECHANICAL PROPERTIES
Melts
Metallic Materials
Nanostructure
NANOSTRUCTURES
Nanotechnology
Nodular graphitic structure
POROSITY
POWDERS
Silicon
SILICON OXIDES
SOLIDIFICATION
Structural Materials
Studies
Surfaces and Interfaces
THIN FILMS
WATER
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Summary:This study investigated the reasons for the irregular structure of primary graphite nodules that were formed in a hypereutectic cast iron powder during water atomization. The graphite nodules contain a significant amount of micron-sized pores and multiple nanometric voids that formed from silicon oxide bifilms. The bifilms theory is often used to explain the mechanisms responsible for the presence of pores in castings. However, even if many results presented in the literature tend to corroborate the existence of bifilms, to this date, only indirect evidences of their existence were presented. The observations presented in this paper are the first to show the double-sided nature of these defects. These observations support the bifilms theory and give an explanation for the presence of porosities in castings. The bifilms were used as substrate for graphite growth during solidification. The irregular structure of the graphite nodules is a consequence of the rather random structure of the bifilms that were introduced in the melt as a result of turbulences on the surface of the melt during pouring. The confirmation of the existence of bifilms can contribute to the understanding of the mechanical properties of various metallic parts.
ISSN:1073-5615
1543-1916
DOI:10.1007/s11663-016-0730-x