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|Title:||Protective Coatings for the Graphite Facing in Calcium-Aluminothermal Processes|
|Publisher:||Estonian Academy Publishers|
|Citation:||Protective Coatings for the Graphite Facing in Calcium-Aluminothermal Processes / N. Obabkov, V. Gorkunov, R. Munter et al. // Proceedings of the Estonian Academy of Sciences. — 2008. — Vol. 57. — Iss. 1. — P. 54-60.|
|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 (Al2O3, Al2O3-CaO, ZrO2, NbC, Al2O3 + 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).|
|metadata.dc.description.sponsorship:||The financial support to V. G. from the Doctorate School of the Faculty of Chemical and Materials Technology of Tallinn University of Technology is gratefully acknowledged.|
|Appears in Collections:||Научные публикации, проиндексированные в SCOPUS и WoS CC|
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