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

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

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

Historical perspective

1914 EtNH3+NO3

-

1980’s Pyridinium eutectic with AlCl3 researched for Al deposition and Al batteries

1990’s Prevalence of imidazolium based cations

2000’s Environmentally more benign ionic liquids

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

Electropolishing

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

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.

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 / IrO2 CathodesTi JigsStandard pump / tank fittingsLess gassingBetter current efficiency

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

Electropolishing

Strategy:

• Polish metal• Vary conditions• Characterise surface• Heat treat

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)

Electropolishing

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

Electropolishing

Fully immersed , polished blade (RR3010)60 mins, total process time.Eapp = 5.8 V

Electropolishing

Fully immersed , polished blade (RR3010)60 mins, total process time.Eapp = 5.8 V

Some trapped shell loosened!

Electropolishing: recycling

Spent polishing liquid from the electropolishing process can be recycled and reused:

(a) Spent liquid(b) Equal volume of water added

SettlementFiltrationHeating (remove water)

(c) Recylced liquid

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 pagesISBN-10: 3-527-31565-9

ISBN-13: 978-3-527-31565-9 Wiley-VCH, Weinheim