Nosov Magnitogorsk state technical university (Magnitogorsk, Russia)

V. M. Kolokoltsev, Dr. Eng., Prof.
E. V. Petrochenko, Dr. Eng., Prof., e-mail: evp3738@mail.ru
O. S. Molochkova, Cand. Eng., Associate Prof.

The paper is devoted to examination of the effect of boron modification and temperature conditions for metal cooling in a mould on phase composition, morphology and chemical composition of structural components of heat- and wear-resistant white cast iron of Fe–C–Cr–Mn–Ni–Ti–Al–Nb system. The phase composition of the metallic base changed from the dualphase (α- and γ-phases) to the completely single-phase (γ-phase). Boron modification influenced on the type of secondary carbides, while secondary hardening in a mould occurs owing to extraction of dispersed niobium carbides (without boron, but owing to chromium carbides). The structure of modified cast iron is presented by the primary complex carbides (Ti, Nb, Cr, Fe) C, as well as by solid solution dendrites, eutectics and secondary carbides MC. Boron addition changes the chemical composition of primary carbides with decrease of niobium content from 44 to 2% and increase of titanium content from 24 to 65%; content of eutectic carbides rises as well. As for hypereutectic carbides, they are characterized by increase of Fe content and lowering of Cr content. Parameters of the primary phases (MC carbides and solid solution dendrites) were investigated using the methods of quantitative metallography. The special technique of Thixomet PRO image analyzer was used for evaluation of the F form factor which is the criterion of compatibility of the primary phases. The following parameters were used in this work as the parameters of dendrite structure: dispersity of the dendrite structure (δ), volumetric part of dendrites (V), distance between the axes of second order dendrites (λ₂), form factor (F), average dimensions of dendrites — square (S), length (l) and width (β). Of the suggested characteristics (parameters) allowed not only to provide quantitative evaluation of the dendrite structure, but also to determine modification degree as relative (in %) variation of the each criterion in modified cast iron in comparison with non-modified iron. Quantitative relation between modification degree and crystallization conditions were established as well.

1. Goldshtein Y. E., Mizin V. G. Inoculation of ferrumcarbon alloys. М.: Metallurgiya. 1993. 416 p.
2. Kolokoltsev V. M., Petrochenko E. V. Metallurgical and metal-science aspects of rising the functional properties of white cast iron products. Vestnik Magnitogorskogo gosudarstvennogo tekhnicheskogo universiteta im G. I. Nosova. 2014. No. 4 (48). pp. 87–98.
3. Tsypin I. I. White wear-resistant cast iron — evolution and prospects. Liteinoe proizvodstvo. 2000. No. 9. pp. 15–16.
4. Bobro Yu. G. Alloyed cast iron. М.: Metallurgiya. 1976. 288 p.
5. Silman G. I. Thermodynamics and thermokinetics of structure forming in cast iron and steels. М.: Mashiniostrornie. 2007. 302 p.
6. Garber M. E. Wear-resistant white cast iron: properties, structure, technology, operation. М.: Mashiniostrornie. 2010. 280 p.
7. Zhukov A. A., Silman G. I., Froltsov M. S. Wear-resistant castings from complex-alloyed white cast iron. М.: Mashiniostrornie. 1984. 104 p.
8. Yoganandh J., Natarjan S., Kumaresh Babu S. P. Erosive Wear Behavior of Nickel-Based High Alloy White Cast Iron Under Mining Conditions Using Orthogonal Array. Journal of Materials Engineering and Performance. 2013. Vol. 22 (9). pp. 2534–2540.
9. Sain P. K., Sharma C. P., Bhargava A. K. Microstructure Aspects of a Newly Developed, Low Cost, Corrosion-Resistant White Cast Iron. Journal of Metallurgical and Materials Transactions A. 2013. Vol. 44F. pp. 1665–1671.
10. Tasgin Y., Kaplan M., Yaz M. Investigation of effects of boron additives and heat treatment on carbides and phase transition of highly alloyed duplex cast iron. Materials and Design. 2009. Vol. 30. pp. 3174–3179.
11. Hufenbach J., Kunze K., Giebeler L., Gemming T., Wendrock H., Baldauf C., Kühn U., Hufenbach W., Eckert J. The effect of boron on microstructure and mechanical properties of high-strength cast FeCrVC. Materials Science & Engineering A. 2013. Vol. 586. pp. 267–275.
12. Chen Xiang, Li Yanxiang. Effect of heat treatment on microstructure and mechanical properties of high boron white cast iron. Materials Science and Engineering A. 2010. Vol. 528. pp. 770–775.
13. Yun-Cheng Peng, Hui-Jin Jin, Jin-Hai Liu, Guo-Lu Li. Effect of boron on the microstructure and mechanical properties of carbidic austempered ductile iron. Materials Science and Engineering A. 2011. Vol. 529. pp. 321–325.
14. Kolokoltsev V. M., Konopka Z., Petrochenko E. V. Zeliwo specjalne rodzaje, odlewanie, obrobka, cieplna, wtasciwosci. Czestochowa. 2013. 185 s.
15. Kolokoltsev V. M., Petrochenko E. V. Structure features and properties of high-alloy white irons. Vestnik Magnitogorskogo gosudarstvennogo tekhnicheskogo universiteta im G. I. Nosova. 2013. No. 5 (45). pp. 3–8.
16. Gromczyk М., Kondracki М., Studnicki А., Szajnar J. Stereological analysis of carbides in hypoeutectic chromium cast iron. Archives of Foundry Engineering. 2015. Vol. 15 (2). pp. 17–22.
17. Petrochenko E. V., Molochkova O. S. Analysis of interaction of chemical composition, cooling conditions during solidification with the features of alloys structure, oxidized surface and properties of complex-alloyed white cast irons. Vestnik Magnitogorskogo gosudarstvennogo tekhnicheskogo universiteta im G. I. Nosova. 2011. No. 4 (36). pp. 50–53.

18. Kolokoltsev V. M., Petrochenko E. V., Molochkova O. S. Structure and properties of heat- and wear-resistant white cast irons of the Cr–Mn–No–Ti system. Chernye metally. No. 3. 2016. pp. 42–48.
19. Petrochenko E. V. Features of forming of structure and properties of complex-alloyed white irons depending on different types of heat treatment. Chernye metally. No. 1. 2012. pp. 10–14.
20. Gurevich Yu. G. Wear-resistant composite material: titanium carbide — white iron. Chernye metally. No. 4. 2010. p. 14.
21. Petrochenko E. V. Features of crystallization, forming of the structure and properties of wear-resistant and heat-resistant irons in different cooling conditions. : thesis of a doct. of techn. sciences. Magnitogorsk. 2012. 310 p.
22. Molochkova O. S. Choice of the composition and investigation of the structure, properties of heat- and wear resistant complexalloyed white cast irons: thesis of a cand. of techn. sciences. Magnitogorsk. 2012. 123 p.