Copper slag is a waste product obtained during matte smelting and refining of copper. The present work explores the coating potential of copper slag by plasma spraying. This work shows that copper slag is eminently coatable. An attempt has been made in the present investigation to use the composites coatings of copper slag and Al powder in suitable combination on aluminium and mild steel substrates in order to improve the surface properties of these ductile metal-alloy substrates. When premixed with Al powder, the coating exhibits higher interfacial adhesion as compared to pure copper slag coatings. Maximum adhesion strengths of about 23？MPa and 21？MPa are recorded for the coatings of copper slag with 15？wt% of Al on aluminium and mild steel substrates, respectively. The input power to the plasma torch is found to affect the coating deposition efficiency and morphology of the coatings. It also suggests value addition of an industrial waste. 1. Introduction Among different surface modification techniques, plasma spraying stands out as one of the most versatile and technologically sophisticated thermal spraying techniques [1–4]. The advantages of plasma spraying include formation of ceramic microstructures with fine, equiaxed grains without columnar defects, deposition of graded coatings with a wide compositional variety, formation of thick coatings with only modest investment in capital equipment, and design capability for free-standing thick forms of monolithic and mixed ceramics in near-net shape configuration. Plasma spray coating is a typical thermal spraying process that combines particle melting, quenching, and consolidation in a single operation. It utilizes the exotic properties of the plasma medium to process different materials. But high cost of spray grade powders limits the adoption of this technique leading to a scope for research on new cost-effective and cheap materials suitable for plasma spray coating. In thermal plasma, it is possible to spray all kind of metallic and nonmetallic materials like metal oxides, carbides, nitrides, and silicides, and so forth [5–9]. Many of these conventional coating materials are relatively expensive, to the extent that cost of spray-grade powders alone can account for 50–60% of the cost of operating plasma spray unit. In recent years, although a large number of investigations have been carried out on production of ceramic coatings using these metal oxides, little efforts have been made in plasma processing of cheap and naturally occurring materials/minerals [10]. Copper slag is such an industrial waste
References
[1]
R. Westerg？rd, L. C. Erickson, N. Axén, H. M. Hawthorne, and S. Hogmark, “The erosion and abrasion characteristics of alumina coatings plasma sprayed under different spraying conditions,” Tribology International, vol. 31, no. 5, pp. 271–279, 1998.
[2]
L. Dubourg, R. S. Lima, and C. Moreau, “Properties of alumina-titania coatings prepared by laser-assisted air plasma spraying,” Surface and Coatings Technology, vol. 201, no. 14, pp. 6278–6284, 2007.
[3]
Z. Yin, S. Tao, X. Zhou, and C. Ding, “Tribological properties of plasma sprayed Al/Al2O3 composite coatings,” Wear, vol. 263, no. 7–12, pp. 1430–1437, 2007.
[4]
R. B. Heiman, Plasma Spray Coating, Principles and Applied Materials, John Wiley, New York, NY, USA, 1989.
[5]
B. H. Robert, Plasma Sprayed Coatings; Principles and Applications, VCH, New York, NY, USA, 1996.
[6]
D. Maejka and B. Benko, Plasma Spraying of Metallic and Ceramic Materials, John Wiley, New York, NY, USA, 1989.
[7]
C. T. Liu and C. L. White, “Design of ductile polycrystalline Ni3Al alloys,” in Proceedings of the Symposium on High Temperature Ordered Intermetallic Alloys, C. C. Koch, C. T. Liu, and N. S. Stoloff, Eds., vol. 39, pp. 365–380, Materials Research Society, Warrendale, PA, USA, 1985.
[8]
R. W. Cahn, “Load-bearing ordered intermetallic compounds—a historical view,” MRS Bulletin, vol. 5, article 18, 1991.
[9]
J. Z. Chen, H. Herman, and S. Safai, “Evaluation of NiAl and NiAl-B deposited by vacuum plasma spray,” Journal of Thermal Spray Technology, vol. 2, article 357, 1993.
[10]
S. C. Mishra, S. Das, A. Satapathy, S. Sarkar, P. V. Ananthapadmanabhan, and K. P. Sreekumar, “Investigation on composite coating of low grade minerals,” Journal of Reinforced Plastics and Composites, vol. 28, no. 24, pp. 3061–3067, 2009.
[11]
K. Al-Jabri, R. Taha, and M. Al-Ghassani, “Use of copper slag and cement by-pass dust as cementitious materials,” Cement, Concrete and Aggregates, vol. 24, no. 1, pp. 7–12, 2002.
[12]
B. Gorai, R. K. Jana, and P. Premchand, “Characteristics and utilisation of copper slag—a review,” Resources, Conservation and Recycling, vol. 39, no. 4, pp. 299–313, 2003.
[13]
S. C. Mishra, K. C. Rout, P. V. A. Padmanabhan, and B. Mills, “Plasma spray coating of fly ash pre-mixed with aluminium powder deposited on metal substrates,” Journal of Materials Processing Technology, vol. 102, no. 1, pp. 9–13, 2000.
[14]
C. R. C. Lima and R.-E. Trevisan, “Graded plasma spraying of premixed metal-ceramic powders on metallic substrates,” Journal of Thermal Spray Technology, vol. 6, no. 2, pp. 199–204, 1997.
[15]
S. P. Sahu, A. Satapathy, A. Patnaik, K. P. Sreekumar, and P. V. Ananthapadmanabhan, “Development, characterization and erosion wear response of plasma sprayed fly ash-aluminum coatings,” Materials and Design, vol. 31, no. 3, pp. 1165–1173, 2010.
[16]
A. Satapathy, S. P. Sahu, and D. Mishra, “Development of protective coatings using fly ash premixed with metal powder on aluminium substrates,” Waste Management and Research, vol. 28, no. 7, pp. 660–666, 2010.
[17]
H. Ageorges and P. Fauchais, “Plasma spraying of stainless-steel particles coated with an alumina shell,” Thin Solid Films, vol. 370, no. 1, pp. 213–222, 2000.
[18]
S. C. Mishra, A. Satapathy, P. V. Ananthapadmanabhan, and K. P. Sreekumar, “Plasma spray coating of red mud on metals,” in Proceedings of Symposium on Power Beams and Materials Processing, pp. 709–712, 2002.
[19]
A. Satapathy, Thermal spray coating of red mud on metals [Ph.D. thesis], National Institute of Technology, Rourkela, India, 2006.
[20]
A. Satapathy, S. C. Mishra, P. V. Ananthapadmanabhan, and K. P. Sreekumar, “Development of ceramic coatings using redmud—a solid waste of alumina plants,” Journal of Solid Waste Technology and Management, pp. 48–53, 2007.
[21]
L. Powloski, The Science and Engineering of Thermal Spraying, Willey, 1995.
