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Prevention of High-Temperature Surface Degradation in SiMo Cast Irons by Cr and Al Alloying
- Source :
- Metallurgical and Materials Transactions B. 51:2542-2554
- Publication Year :
- 2020
- Publisher :
- Springer Science and Business Media LLC, 2020.
-
Abstract
- High silicon molybdenum-alloyed cast irons (SiMo) with spherical graphite are widely used for cast thin-wall exhaust manifolds, worked in high-temperature oxidation environment; therefore, prevention of surface degradation during service is important for such common application. The base SiMo and two alloyed by 1 pct Cr and 3 pct Al cast irons were tested at high temperatures in air and a combustion atmosphere to study the microstructural processes of surface degradation. It was shown that surface degradation of SiMo cast irons involves several microstructural processes, including the formation of multilayered oxide scale and development of internal porosity, resulting in decarburization of graphite nodules. Monitoring weight change of the specimens and Leco C analysis were used for decoupling the rates of surface oxidation and metal matrix decarburization. SEM/EDX analysis was used to study the phase composition of scale and high-resolution TEM analysis was performed to determine the detailed information about the atomic structure of protection layers formed on scale/metal matrix interface. The results were used to qualify and link different surface degradation mechanisms. In the base SiMo cast iron, the protection efficiency of formed amorphous silica layers is limited by intensive decarburization at temperatures above 700 °C. It was shown that Cr and Al alloying prevents surface degradation and suppresses decarburization by developing thermally stable oxide films on metal-scale interface, thus allowed to increase a safe working temperature up to 800 °C in air and the combustion atmosphere.
- Subjects :
- 010302 applied physics
Decarburization
Materials science
Silicon
Metallurgy
0211 other engineering and technologies
Metals and Alloys
Oxide
chemistry.chemical_element
02 engineering and technology
engineering.material
Condensed Matter Physics
Combustion
01 natural sciences
chemistry.chemical_compound
chemistry
Mechanics of Materials
0103 physical sciences
Materials Chemistry
engineering
Degradation (geology)
Graphite
Cast iron
Porosity
021102 mining & metallurgy
Subjects
Details
- ISSN :
- 15431916 and 10735615
- Volume :
- 51
- Database :
- OpenAIRE
- Journal :
- Metallurgical and Materials Transactions B
- Accession number :
- edsair.doi...........1ba56fb6157755f58b8741a1058abbe7