View source for Physics:Ductile iron with special properties

'''Ductile Iron with special properties''' is a form of malleable [[Chemistry:Cast iron|cast iron]] (DITG type - ductile iron developed by S&P Group TRIBOFATIGUE Ltd and JSC Gomselmash) which possess a complex of high [[Chemistry:List of materials properties#Mechanical properties|mechanical properties]]: [[Physics:Strength of materials|strength]] and [[Physics:Plasticity|plasticity]], crack and contact [[Fatigue (material)|fatigue]] resistance, self-lubrication at [[Physics:Friction|friction]] and ability to dampen the dynamic loading. The following specific feature can be seen in the "strength vs plasticity" diagram: plasticity increases with the increase in strength. Such properties can be explained by the balanced chemical composition with an optimal ratio of three modifying elements: [[Chemistry:Molybdenum|Mo]]-[[Chemistry:Nickel|Ni]]-[[Chemistry:Copper|Cu]] (that's why the DITG material is called MONICA) and are assured by the corresponding [[Physics:Microstructure|microstructure]] which is obtained by the respective [[Physics:Heat treating|heat treatment]].
== Chemical composition ==

The chemical composition corresponds to high-strength [[Chemistry:Cast iron|cast iron]] with spherical [[Chemistry:Graphite|graphite]] (DI, ADI), but with the total [[Physics:Equivalent carbon content|carbon equivalent]] of about ''СE'' = 5.0 … 5.5. For three elements (Mo-Ni-Cu) this equivalent is equal to ''СE''<sup>(3)</sup> = 0.35…0.45.

== Microstructure ==
Depending on the [[Physics:Heat treating|heat treatment]] modes, the [[Physics:Microstructure|microstructure]] characteristic of [[Chemistry:Austempered Ductile Iron|ADI]] is obtained; it possesses the following specific feature: under certain conditions [[Chemistry:Molybdenum|molybdenum]] evolutions are formed.

== Mechanical properties ==

At [[Physics:Strength of materials|strength]] limit σ<sub>u</sub>~1300…1400 MPa the [[Physics:Plasticity|plasticity]] reaches the values of 3…5 %. Critical coefficient of intensity of [[Physics:Stress (mechanics)|stresses]] is equal to ''K''<sub>''c''</sub>=60…75 MPa<math>\sqrt[2]{m}</math> at σ<sub>u</sub>=1100…1200 MPa. The contact [[Fatigue (material)|fatigue]] limit (under the conditions of initial point contact) is ''p''<sub>''f''</sub>=3750 MPa based on the tests of 10<sup>8</sup> cycles. High resistance to [[Fatigue (material)|fatigue]] is explained by the fact that modification with [[Chemistry:Molybdenum|molybdenum]] is more effective than the one with [[Chemistry:Nickel|nickel]] and [[Chemistry:Copper|copper]]: in order to obtain the steel bending fatigue limit with rotation of σ<sub>−1</sub>=150 MPa, the amount of [[Chemistry:Nickel|nickel]] shall be approximately 10 times higher than the amount of [[Chemistry:Molybdenum|molybdenum]].

== Wear resistance ==

MONICA displays high self-lubrication properties since its [[Physics:Microstructure|microstructure]] contains [[Chemistry:Graphite|graphite]], [[Chemistry:Molybdenum|molybdenum]] and [[Chemistry:Copper|copper]]. Availability of these elements helps to reduce the coefficient of [[Physics:Friction|friction]] for MONICA to ~50…70 % (as compared to steel) and to decrease the [[Physics:Wear|wear]] to ~30…50 %.

== Application ==

The material is used to manufacture the parts of critical heavily loaded tribo-fatigue systems (see, for example, Figure 1).<ref>Rundman, K. B., Moore, D. J., Hayrynen, K. L., Dubensky, W. J., & Rouns, T. N. (1988). The Microstructure and Mechanical Properties of Austempered Ductile Iron. J. Heat Treat., 5(2), 79-85. Retrieved May 23, 2019.</ref><ref>Sosnovskiy, L. A. Iron and steel in tribo-fatigue systems of modern machinery and equipment / L. A. Sosnovskiy, P. A. Vityaz, V. A. Gapanovich, N. V. Psyrkov, N. A. Makhutov // Mechanics of machines, mechanisms and materials. – 2014. – № 4 (29). – P. 5–20. (In Russian).</ref><ref>Sosnovskiy, L. A. Experimental construct a complete pair «VCHTG ductile iron / steel 18HGT» rolling fatigue curve and its analysis / L. A. Sosnovskiy, V. V. Komissarov, E. S. Taranova, S. A Tyurin // Mechanics of machines, mechanisms and materials. – 2014. – № 1 (26). – P. 32–39. (In Russian).</ref><ref>Sosnovskiy, L. A. New structural material for railway rails: mechanical and service properties / L. A. Sosnovskiy, V. V. Komissarov, V. I. Matvetsov, N. E. Miroshnikov // Bulletin of BelSUT. – 2014. – № 2 (29). – P. 77–82. (In Russian).</ref><ref>Komissarov, V. V. On the experience of manufacturing and operation of gears from the new structural material «MONICA» / V. V. Komissarov, E. S. Taranova,  P. S. Drobyshevskiy, V. O. Zamyatnin, S. A. Tyurin, L. A. Sosnovskiy // Bulletin of IzhGTU name M. T. Kalashnikov. – 2017. – V. 20. – № 2. – P. 107–112. (In Russian).</ref>

[[File:cast_iron_MONICA-4.jpg|thumb|<div style="text-align: center;"> Figure 1 – A heavy freight train (train weight 3000 tons) goes along the experimental R65 rails made of MONICA (shown by arrow)</div>|alt=]]

== References ==
{{Reflist}}

[[Category:Materials science]]
[[Category:Ferrous alloys]]
[[Category:Metallurgy]]

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