Removal of casting defects from CMSX-4^® and CMSX-10^® alloys by electropolishing in a novel electrolyte; Deep Eutectic Solvent

¹ Rolls-Royce plc, Elton Road, PO. Box 31, Derby DE24 8BJ, UK
² Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
³ Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK

Abstract

Here we describe the use of environmentally benign Deep Eutectic Solvents (DESs) to electropolish oxide casting scale from Ni based superalloy turbine blades. These new electrolytes are a viable alternative to hazardous and aggressive aqueous acids and etchants currently used to process these components. In addition we show that the DES electrolytes selectively expose the underlying surface structure of these superalloys. We demonstrate the ability of these electrolytes to preferentially etch either γ or γ′ phases depending on the choice of electrolyte formulation and the applied potential during the electrolytic etch on CMSX-4^® and CMSX-10^® alloys.