Recycling of Alumina Power After Plasma Spraying
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Vol. 61, No. 2, July, 2020
RECYCLING OF ALUMINA POWER AFTER PLASMA SPRAYING A. V. Stepnov,1 I. V. Belyaev,2,4 V. E. Bazhenov,3 A. A. Pavlov,2 and A. V. Kireev1 Translated from Novye Ogneupory, No. 4, pp. 24 – 27, April, 2020.
Original article submitted December 23, 2019. The possible reuse of powder Al2O3 waste formed in manufacturing of ceramic refractory products by plasma spraying was studied. The powder alumina waste was found to be individual particles a- and g-Al2O3 and their conglomerates and also included iron oxides in the form of Fe2O3 and Fe3O4. It was shown that the plasma-spraying powder waste had to be purified of Al2O3 conglomerates and iron oxides in order to reuse it. For this purpose, powder waste should be sifted through a sieve and subjected to magnetic separation. It was established experimentally that such a powder can be reused for applying coatings and fabricating products by plasma spraying without degrading their quality. Keywords: plasma spraying, powder Al2O3 waste, magnetic separation, recycling.
INTRODUCTION
EXPERIMENTAL
Cost reduction and increased utilization coefficients for starting raw materials are important issues of any production. Reuse of production waste itself is one method for resolving these issues. This can not only decrease the intrinsic product cost but also improve the environmental friendliness of the production. About 40 mass% of the starting powder for spraying is wasted during fabrication of ceramic products of pure Al2O3 by plasma spraying. Most of this waste consists of Al2O3 particles that pass through the plasma but are not impacted by the mandrel (master-model). Reliable information on the granulometric and phase compositions of this waste and the presence in it of hazardous side impurities has not been published. All this does not allow existing powder waste to be directly used in plasma spraying technology without any preparation. The present work studied the possible reuse of spent Al2O3 powder in plasma spraying technologies.
The material for plasma spraying of products was a-Al2O3, i.e., white electrocorundum grade 25A, as fractured powder with average particle size 32 mm (Fig. 1). The plasma spraying process was performed using a UPN-350 unit (Russia). The plasma-forming gas was compressed air. The plasma spraying parameters were constant: plasmotron arc current 125 – 130 A, voltage 200 – 210 V, plasma-forming gas (air) pressure 0.5 MPa, spraying distance 200 mm, and plasmotron displacement rate along the sprayed surface 20 mm/sec. The plasma spraying technology was described in detail before [1 – 5].
1 2 3
4
Plasma Spraying Center LLC, Vladimir, Russia. A. G. and N. G. Stoletov Vladimir State University, Vladimir, Russia. National University of Science and Technology MISiS, Moscow, Russia and Plasma Spraying Technologies LLC, Vladimir, Russia. [email protected]
Fig. 1. Powder used to fabricate plasma-sprayed products.
196 1083-4877/20/06102-0196 © 2020 Springer Science+Business Media, LLC
Recycling of Alumina Power After Plasma Sprayi
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