headerpos: 12198
 
 
 

Proceedings of the Estonian Academy of Sciences

ISSN 1736-7530 (electronic)   ISSN 1736-6046 (print)
Formerly: Proceedings of the Estonian Academy of Sciences, series Physics & Mathematics and  Chemistry
Published since 1952

Proceedings of the Estonian Academy of Sciences

ISSN 1736-7530 (electronic)   ISSN 1736-6046 (print)
Formerly: Proceedings of the Estonian Academy of Sciences, series Physics & Mathematics and  Chemistry
Published since 1952
Publisher
Journal Information
» Editorial Board
» Editorial Policy
» Archival Policy
» Article Publication Charges
» Copyright and Licensing Policy
Guidelines for Authors
» For Authors
» Instructions to Authors
» LaTex style files
Guidelines for Reviewers
» For Reviewers
» Review Form
Open Access
List of Issues
» 2019
» 2018
» 2017
» 2016
» 2015
» 2014
» 2013
» 2012
» 2011
» 2010
» 2009
» 2008
Vol. 57, Issue 4
Vol. 57, Issue 3
Vol. 57, Issue 2
Vol. 57, Issue 1
» Back Issues Phys. Math.
» Back Issues Chemistry
» Back issues (full texts)
  in Google. Phys. Math.
» Back issues (full texts)
  in Google. Chemistry
» Back issues (full texts)
  in Google Engineering
» Back issues (full texts)
  in Google Ecology
» Back issues in ETERA Füüsika, Matemaatika jt
Subscription Information
» Prices
Internet Links
Support & Contact
Publisher
» Staff
» Other journals

Protective coatings for the graphite facing in calcium–aluminothermal processes; pp. 54–60

(Full article in PDF format) doi: 10.3176/proc.2008.1.06


Authors

Nikolai Obabkov, Valeri Gorkunov, Rein Munter, Askold Beketov

Abstract

Results of pilot plant and full scale studies on the elaboration of high temperature protective coatings for graphite in the process of the reductive melting of niobium pentoxide and NbAl alloys production are presented. Graphite has found extensive application in high temperature processes due to its unique thermophysical properties. However, in these conditions it reacts very easily with air oxygen, liquid metals, oxides, and fluorides. As a result, porous graphite gets impregnated with liquid metal; besides, carbonization of melt and formation of a layer of metal carbides on graphite surface takes place. The layer of metal carbides has a low adhesion with graphite and a major part of them is transferred to the melt. The graphite facing of a furnace is quickly destructed. To avoid these harmful processes, special plasma sprayed protective coatings are used.In this work various coatings (Аl2О3, Аl2О3·CaO, ZrO2, NbC, Аl2О3 + Nb, ZrO2 + Nb, NbC + Nb, Nb) were tested in pilot plant and industrial conditions. It was established that the best durability of the protective coating on graphite can be achieved in the case of its three-layer composition: Nb (0.07 mm) + NbC (0.4 mm) + Nb (0.3 mm). After industrial melting of 500–2000 kg ingots about 80% of this coating on the belt of the shaft furnace had preserved. Plasma sprayed protective coatings on the graphite facing extended its operation time, reduced the carbon content in the metal ingots to 0.02% (mass), and slag carbon content to 0.05–0.15% (mass).

Keywords

chemical technology, metallothermy, graphite facing, protective coatings.

References

  1. http://www.silmet.ee 29.10.2007.

  2. Plotnikov , V. , Parshin , A. & Gorkunov , V. Elaboration of a calciumalumothermal method for the production of tantal and alloys on the basis of niobium and tantal. Report VNIIHT. Moscow , 1984 (in Russian).

  3. Datta , S. , Klusek , Z. , Kozlovjwski , W. & Burnell-Gray , J. Corrosion in nanotechnology. CorrosionManage. , 2001 , 42 , 24–32.

  4. Samsonov , G. & Öpik , A. Temperature Resistant Coat­ings. Metallurgiya , Moscow , 1973 (in Russian).

  5. Phase diagrams of twin metallic systems. Handbook. Vol. 3. No. 1 (Lyakishev , N. , ed.) Mech. Eng. (Moscow) , 2001 , 123(706) , 737–739 (in Russian).

  6. Hasui , A. Technology of Spraying. Mashinostroenie , Moscow , 1975 (in Russian).

  7. Kindzheri , V. Measurements at Higher Temperatures. Меtallurgizdat , Мoscow , 1963 (in Russian).

  8. Baklanov , V. , Zhdanov , V. & Malysheva , E. Experimental studies on avoiding reactions of melt components with carbon. Institute of Nuclear Centre , Kazakhstan , 2004. http://polar.mephi.ru/ru/conf/2004/ (in Russian).

  9. Kostikov , V. & Shesterin , J. Plasma Sprayed Coatings. Меtallurgiya , Moscow , 1978 (in Russian).

10. Galkin , J. & Guseva , N. Reactions of resistant oxides with graphite during spraying. Fiz. Khim. Mater. Obrab. , 1972 , 3 , 94–96 (in Russian).

11. Kudinov , V. Plasma Sprayed Coatings. Nauka , Moscow , 1977 (in Russian).

12. Sinkovski , A. & Zemskov , G. Coatings of Silicium Carbide on Graphite. Nauka , Leningrad , 1968 (in Russian).

13. Dergunova , V. & Kravetski , G. Graphite Coatings for Construction Materials. Nauka , Leningrad , 1979 (in Russian).

14. Burykina , A. & Evtushok , T. Coatings of Resistant Compounds on Graphite. Nauka , Leningrad , 1967 (in Russian).

15. Zhabreev , V. , Sazonova , M. & Efimenko , L. Enhancement of protective coatings on graphite by including into the composition ZrB2–MoSi2 nanoparticles of SiO2. In Theses of the 4th Internat. Conf. on Chemistry of Solid Materials and Contemporary Micro- and Nano­technologies. Kislovodsk–Stavropol , Severnyj Kav­kaz , 2004 , 72–74 (in Russian).

16. Gorkunov , V. & Munter , R. Calcium-aluminothermal pro­duction of niobium and mineral composition of the slag. Proc. Estonian Acad. Sci. Chem. , 2007 , 56 , 142–156.

17. Beketov , A. , Panteleev , S. & Gorkunov , V. Elaboration of the composition of protective coatings and their plasma spraying onto graphite facing of a shaft furnace. Report NIR. Ural Technical University , Sverdlovsk , 1984 (in Russian).

18. Beketov , A. , Bogoyavlenskij , G. & Gorkunov , V. Elabora­tion of protective plasma coatings for graphite for reductive meltings of niobium , tantal and rare metal alloys. Report NIR. Ural Technical University , Sverd­lovsk , 1987 (in Russian).

19. Allen , A. Temperature Resistant Inorganic Coatings. Khimiya , Leningrad , 1976 (in Russian).

20. Adler , J. , Markova , E. & Granovski , J. Planning of Experi­ments in Search for Optimum Conditions. Nauka , Moscow , 1976 (in Russian).

21. Semchenko , G. , Shuteeva , I. & Splechenko , O. Protection of graphite and graphite containing materials from oxidation. Novye Ogneupory. , 2005 , 7 , 25–26 , 30–31.
 
Back

Current Issue: Vol. 68, Issue 3, 2019




Publishing schedule:
No. 1: 20 March
No. 2: 20 June
No. 3: 20 September
No. 4: 20 December