Deposition of Redmud-Graphite Coating on Metals by Plasma Spraying

Abstract

Plasma Spraying is a versatile technique, which has the advantage of being able to deposit metals, ceramics and/or a combination of these, and generating a homogeneous coating and with required microstructures. In the present work, an abundantly available industrial waste viz. redmud (the waste generated in the aluminium extraction industry) and graphite were taken, pre-mixed in a definite proportion and the mixture spray coated on commercially available aluminium and copper metals. These coatings were deposited at different operating power levels i.e. at 6. 9. 12 and 16 KW of the plasma torch and then were characterised. It is observed that the quality and structure of the coating arc greatly affected by the input power to the torch. The coating adhesion strengths for different samples were determined by standard pull-out method. A maximum interface bonding strength of ~14 MPa was recorded. It was also observed that adhesion of the coating onto the substrate has been improved with the mixing of graphite powder to redmud. Coating morphologies were studied by scanning electron microscopy.