1. Applications of Green Technology in the Manufacture of Turbine Blades Karl S. Ryder Scionix Laboratory, Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK k.s.ryder@le.ac.uk

2. Contents What is an ionic liquid Eutectic-based ionic liquids and how to make them Applications  Immersion Ag for PCB's  Cr plating  Al Plating  Battery applications Electro polishing RS Industrial Fellowship scheme Results (RR3010 blades), XPS Closing remarks

3. Ionic liquids: definition Ionic material that melts below 100 ºC Unusual solvent properties Very low / negligible vapour pressure - do not evaporate Most liquids thermally stable >200 ºC Immiscible with many organic solvents Some have wide potential windows Large and unsymmetrical ions -> low lattice energy and hence low melting point

4. Historical perspective 1914 EtNH 3 + NO 3 - 1980’s Pyridinium eutectic with AlCl 3 researched for Al deposition and Al batteries 1990’sPrevalence of imidazolium based cations 2000’s Environmentally more benign ionic liquids

5. Liquid preparation 10 ILs have been produced in over 200 kg batches One IL made on the tonne scale (for electropolishing) Just mix two components (often r.t. solids) to make liquid! Endothermic reaction, entropy driven

6. Electropolishing Electrochemical dissolution: ChCl / EG liquid High current efficiency Low toxicity No strong acids Comparable finish

7. Electropolishing Pilot plant  Functional process line  Pre treatment  Process, 50 L IL  Rinse Works very well for 300 series stainless steels and high value performance alloys, Ni / Co, Ti etc.

8. Electropolishing Better surface finish (market) Non-corrosive (social) Benign liquid – ChCl/glycol (social) Improved current efficiency (>80%) (economic) Less gas evolution (environmental) Metal recoverable (environmental) SS or Ti / IrO 2 Cathodes Ti Jigs Standard pump / tank fittings Less gassing Better current efficiency

9. Electropolishing Royal Society Industry Fellowship (KSR) Started July 2010: Explore electropolishing of superalloys with IL processes Study composition of alloy Determine etch rate Explore removal of scale (effect on surface melting) Explore removal of casting shell

10. Electropolishing Strategy: Polish metal Vary conditions Characterise surface Heat treat

11. Electropolishing; surface characterisation Electropolish Sample 1 (pale) Electrolytic polishing in IL removes virtually all residual shell. First results suggest alloy composition is not effected by etch Surface roughness greatly reduced Ni(3p)

12. Electropolishing Partially immersed, polished blade (RR3010) 20 mins process time.

13. Electropolishing Fully immersed, polished blade (RR3010) 60 mins, total process time. E app = 5.8 V

14. Electropolishing Fully immersed, polished blade (RR3010) 60 mins, total process time. E app = 5.8 V Some trapped shell loosened!

15. Electropolishing: recycling Spent polishing liquid from the electropolishing process can be recycled and reused: (a) Spent liquid (b) Equal volume of water added Settlement Filtration Heating (remove water ) (c) Recylced liquid

16. Conclusions Electropolishing of superalloy turbine blades in DES type (choline chloride based) ionic liquids: Effective in removing Ni-based surface scale Effective in removing residual shell Homogeneous dissolution of metal Isotropic etching (semi-quantitative XPS) Reducing surface roughness Softening / loosening trapped shell Visualising grain structure possible prior to heat treatment possible by electrolytic etch. This has the potential to save process time and reduce production costs. Hard back, 338 pages ISBN-10: 3-527-31565-9 ISBN-13: 978-3-527-31565-9 Wiley-VCH, Weinheim