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Plasma sprayed fly ash coating on metal substrates

Alok Satapathy, Suvendu Prasad Sahu, Debadutta Mishra, Amar Patnaik

Rich in metal oxides, fly ash has tremendous potential to be utilized as a coating material on structural and engineering components. Fly ash is basically a solid waste generated in huge quantities from coal fired thermal power stations during the combustion of coal. This work aims at developing and characterizing a new class of such coatings made of fly ash by a novel technique like plasma spraying. Plasma spray technology has the advantage of being able to process various low-grade-oreminerals to obtain valueadded products and also to deposit ceramics, metals and a combination of these, generating near-homogenous coatings with the desired microstructure on a range of substrates. In the present investigation, coatings are developed on aluminumsubstrates usingmixtures of fly ash pre-mixed with aluminum powder in different weight proportions at various plasma torch power levels ranging from9 to 18 kWDC. The coatings are characterized in terms of micro-hardness, interface adhesion strength and deposition efficiency. Maximumadhesion strength of about 35MPa is recorded with coatings deposited at 12 kW power level. It is noticed that the quality and properties are significantly affected by the operating power level of the plasma. This work establishes fly ash as a potential coating material, suitable for possible tribological applications.