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Coatings Technology for Gas Turbines – Past, Present and Future Challenges

Parsons 2011: 5-8 September 2011

D S Rickerby

Corporate Specialist

Surface Engineering

Rolls-Royce plc

Derby, UK




Structure of the presentation

Importance of surface coatings to the product

development process.

Integration of surface engineering into the

design process and the move to predictive

design

Simulation and robust design

Future Challenges

Summary



Broadening our portfolio



Early benefits of surface engineering –Corrosion protection

Performance penalty of ca. 5% at

take off which approached the limit

of acceptability for a twin-engined

turboprop aircraft

Increase in specific fuel consumption

of up to 2% which represented a

significant cost penalty for the

operators.

Surface engineering became an

essential and very competitive issue

in the aerospace industry.

Service run Nimonic 108 HPTB‟s



Coating/Process Applicability

Oxidation

Coatings

Corrosion

Coatings

Thermal Barrier

Coatings

Tribological

Coatings



Coating/Process Applicability

Oxidation

Coatings

Corrosion

Coatings

Thermal Barrier

Coatings

Tribological

Coatings

Coating Systems are becoming more complex to

match Design intent.

Important to understand current manufacturing

capability in line with engineering specifications.

Manufacturing capability must be deployed on a

global network – reduction in empirical knowledge.

Simulation/validation of the systems capability will

be central to lifing method development and cost

optimisation.



Cycles to meet future performance targets

N Arndt, Environmentally friendly aero-engines for the 21st

century, CEAS Berlin, 12 September 2007

M Oechsner, Property variation in TBC systems and their impact on

turbine design, TBC III Irsee Germany, 7-12 August 2011

*

*

+

+

For both industrial and aero gas

turbines the key factors which drive

the design process are:

Higher cycle temperatures

Increased pressure ratio



2100

1900

1700

1500

1300

1100

900

Uncooled

blades

Cooled

blades

ACARE

Production

technology

Date

SC cast

DS cast alloys

Conventional Cast alloys

Wrought alloys

Tu

rbin

e E

ntr

y T

em

pera

ture

(K

)

1940 1960 1980 2000 2020

W1Dart

Avon

Conway

Spey

RB211

Trent

Type-Test turbine entry temperature (TET) trend and progress in turbine materials and technology

Demonstrator

technology

Coated

blades

V20 CMC‟s



Predictive

Design

Reactive

DesignToday

From To

Evolving design requirements Defined design requirements

Extensive development trials Controlled parameters

Product performance assessed

by ‘ build and test’

Product performance

modelled and simulated

Empirical understanding Data driven environment

Performance and production

problems fixed after product in use

Designed for robust

performance and production

Quality ‘tested in’ Quality ‘designed in’



Reactive versus predictive design

Re

so

urc

es

Req

uir

ed

Re

ve

nu

e G

en

era

ted

Revenue

predictive

design

Revenue

reactive

design

Launch Launch Time

Current and Future Designs

- Predictive Design

- Early Problem Identification

- Solution when costs are low

Early Engine Designs

- Reactive Design

- High Costs



Broadening our portfolio

Underpinning long-term growth



The aero engine market has never been more competitive

Mature industry, limited scope for technology advancement

Product differentiation is by being

First to produce a suitable engine for the market

Best specification to the customer

Engine development cycle in line with that of the customer.

Product life cycle covers all activities from the generation of the initial product concept and business case through to product entry into service and beyond into its service life.

Use of generic designs to existing and new products using proven technology.

Capability acquisition activity to secure future technology requirements.

Need to reduce the variation in the performance of surface engineered components.

The product life cycle



Technology innovation lifecycle

Stage 1

Product Planning

Stage 2

Full Concept

Definition

Stage 3

Product

Development

Stage 4

In-Service

Management

Capability Acquisition

MCRL/TRL

1

Manufacturing Capability Readiness Levels (CRL)

2 3 4 5 6 7 8 9Technology Assessment & Proving Pre-Production Production

Business

Led

Preliminary

Launch

Full

Launch

Product

Delivery



Corrosion in HPT Discs TETs have increased

Salt land on the compressor blades and condenses

Salt sheds and enters the cooling airstream which washes the HPT

disc

Hot corrosion and high temperature corrosion-fatigue occurs

Generic industry wide issue

Pitting from sulphidation can cause premature fatigue crack initiation

Development of Coatings to Protect Powder Metallurgy Turbine Disks from Hot Corrosion Attack, S. L. Draper, J. Telesman, T.P. Gabb, and C. Sudbrack, NASA –Glenn

Research Center, L. Underwood and B. Hazel, GE Aviation, Information from AAD NNC07CB73C Contract Final Report, D. Raybould, D. Rice, T. Strangman, and J.

Neumann, Honeywell Aerospace



Current investigations and future challenges

Developing infrastructure for corrosion-fatigue testing

Understanding the controlling parameters of the mechanism

Industry investigating Sol Gel based coatings

The benefits and role of shot peening

Lowering stresses and temperatures locally in disc features

Development of mechanistic models to predict life

Development of Coatings to Protect Powder Metallurgy Turbine Disks from Hot Corrosion Attack, S. L. Draper, J. Telesman, T.P. Gabb, and C. Sudbrack, NASA –Glenn

Research Center, L. Underwood and B. Hazel, GE Aviation, Information from AAD NNC07CB73C Contract Final Report, D. Raybould, D. Rice, T. Strangman, and J.

Neumann, Honeywell Aerospace



A range of validation rigs are now used to assess different geometry, surface treatments and coatings to support further extensions in component life.

Such rigs form the basis for establishing a design for process excellence approach to the introduction of new system concepts.

These to be coupled to robust but innovative manufacturing methods.

Simulating Service Environments M J Ward, S T Halliday and J Forden, Proc. IMechE Part B

J. Engineering Manufacture. In press

*

*



Smart coating concepts

1

2

3

J R Nicholls and B Bordenet, Materials for Advanced Power

Engineering , Proceedings of the 8th Liege Conference Part

III, Energy Technology Band/Vol 53 p 1696.



Hot corrosion performance of „Smartcoat‟ systems

Platinum Aluminide (CN91)

SmC 155

0

20

40

60

80

100

120

140

160

platinum aluminide RT22

Over-aluminised MCrAlY

Smartcoat SmC155

Co

atin

g L

oss (

mm

)

700 C 800 C

J R Nicholls and B Bordenet, Materials for Advanced Power

Engineering , Proceedings of the 8th Liege Conference Part

III, Energy Technology Band/Vol 53 p 1696.



Cracking of MCrAlY environmental systems

U Tack, Fracture Mechanics Aspects of MCrAlY, Turbine

Forum 2010, Nice France, 22-24 September 2010.



Mechanical testing - Comparison of TMF loops

D S Rickerby, International Conference on Metallurgical

Coatings and Thin Films, San Diego CA, 23-27 April 2007.



TMF performance as TBC bond coats

Hot spot condition – R= -infinity, phase angle -135,

compressive strain 0.7% with temperature

cycle1050/250C.

For the Pt-Al, cracks initiated in the diffusion zone whilst

those in the g/g ‘ coating initiated at the surface.

The ceramic top coat prevents rumpling in the MCrAlY

bond coat.

TMF penalty for various bond coats

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

CMSX-4 LCBC PtAl MCrAlY

Str

ain

ra

ng

e C

ap

ab

ilit

y P

en

alt

y (

%)

g/g ‘

Blade showing rumpling following

ceramic loss

Blade showing no rumpling where

ceramic has remained adherent.

D S Rickerby, International Conference on Metallurgical




Engine versus thermal shock testing

U Tack, Fracture Mechanics Aspects of MCrAlY, Turbine

Forum 2010, Nice France, 22-24 September 2010.

*

*D S Rickerby, International Conference on Metallurgical


+ +

+

Strong coating Weak coating



Improving the processes reduce variability

Reproducible processes capable of

deployment on more complex coating

systems

Cost effective manufacturing

Global reach with embedded quality

culture



Product lifecycle management (PLM)

Driven by need to improve

Leadtime, Cost, Quality

Focuses on managing output to

the customer through the lifecycle

Master Model and Geometry management

Live Interface Management

High geometric parametricity, for efficient geometry re-use

Enables Design for Process Excellence and Standard Features.

Linked to Engineering standards defining functionality.



Reducing Variation



Robust design –Turbine disc rim design

main

influence:

front rim

mass flow

12

3

4

Improved System

robustness, reduced

thermal strain rangeTemperature Variation

Datum range

Lower

Level

Upper

Level

Half range

Lower

Level

Upper

Level

5



Continuous improvement



Damping of HP turbine blade

Interlocking shrouds are used

to reduce the risk of HCF

failures from cantilever

vibration modes – resonant

excitation or flutter.

Evolved design optimised with

improved materials and

shroud interlock angle.

Hard facing materials applied to interlock abutment

faces to achieve balance of load/temperature/wear

capability.

Developed high frequency / high temperature rigs

to reproduce service wear mode(s).

Optimum wear behaviour identified for like-on-

like couplesD Stewart and D S Rickerby, Institute of Materials – High

Temperature Wear and Erosion, Derby UK, 10 November 2010.



Plain shrouds give performance

and cost benefits

Modern computer aided analysis

techniques enable current blades

to be designed with low risk of

blade failure from vibration

without the need for interlock

shrouds

The effect of blade cantilever

modes are now assessed in the

early stages of any new design.

Damping of HP turbine blade

Damping, aerofoil shape, blade relative stiffness, NGV forcing and other

design factors all optimised to achieve the required modal frequency

separation.

Interlock coatings removed reducing component cost.D Stewart and D S Rickerby, Institute of Materials – High

Temperature Wear and Erosion, Derby UK, 10 November 2010.



Weibull plots of TBC spallation life – Variation in performance with bond coat chemistry.

0.01 0.1 1.0 10

99.9

0.1

0.2

0.5

1.0

2.0

5.0

10.0

20.0

50.0

30.0

40.0

60.070.080.090.0

99.0

95.0

Weib

ull

Cum

ula

tive D

istr

ibution F

unction

Relative Life

g/g „ Bond Coat

Pt-Al Bond Coat



Weibull plots of TBC spallation life – Future requirements for prime reliance.

Alumina scale quality – growth rate,

stress

Interface stability – S and reactive

elements

Systems design – coating and

method variation



The future for manufacturing processes –Linked to design methods

The move to Robust CoatingsFundamental Coating

Understanding

Coating System Design

Robust Manufacturing Process

Cost Effective System

Performance

Coating Life Cycle



What will Customers want from our next Products ?

Improvement of Performance and Weight

Environmental impacts – Noise versus efficiency

Inventive yet robust

Improvement of reliability, even safer products

Systems Robustness, insensitive to variation or external influences

Quicker and cheaper



Future Trends

C G Levi. IEUVI Optics contamination and lifetime workshop, San Diego CA,

10 November 2005

D S Rickerby et al. Turbine Forum 2010, Nice

France, 22-24 September 2010

K Von Niessen . Turbine Forum 2010, Nice

France, 22-24 September 2010

D S Rickerby . IMFair 2011,

The Institute of Metal

Finishing, Cosford UK, 14-16

June 2011



Summary

Surface engineering usage will continue to grow with increasing

reliance being placed on coatings or surface treatments to achieve

the reliability and performance targets for turbine components.

To further improve the efficiency and fuel consumption in the next generation of gas turbines greater emphasis will be placed on:

Optimisation of current coating systems to manage performance, cost and environmental impact.

Further advances in Quality - First Time initiatives through improved Production Systems

Development of new materials and processes with reduced lead time to market at managed levels of risk.

Further integration at the component design stage and extensive use of modelling/simulation to expedite material and process development to minimise cost and development time.



The Challenge for the Community -“Coping with Conflict”

Less rework

on time

delivery

Improved

Quality and

Performance

Cheaper

to make

Reduced

environmental

impactQuicker to

market and

robust

Global reach

Proactive

Skills gap Technology

innovation

coatings technology for gas turbines past, present and ... 0900...industry investigating sol gel...

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