VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD

Creep and

creep-fatigue

VTT ProperScan® HT Life

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Creep?

= time dependent deformation of solids at T ≥ ½·Tm

Important for:

Design of high temperature applications

Creep strength /stress for

Time to rupture

Time to 1% strain

Weld strength factors (welds)

Life management

Creep damage accumulation

Remaining life estimation

Inspection scheduling

Failure analysis

Ends ultimately in failure (creep rupture)

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Creep limits life in design and service!

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High temperature materials mechanical testing

facilities

16 single specimen creep testing machines (max 950’C)

Uniaxial creep, notched bar, compact tension specimens

4 multi-specimen creep machines (4 specimens each)

3 servo-mechanical testing machines used for:

Impression creep testing

Creep-fatigue under four point bending

Small punch

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High Ni

(Kimura 2012) Temperature compensated creep

to rupture and Wilshire model

curve for nickel-base superalloy

Creep strain and creep strain rate:

VTT in-house LCSP-model

Creep: Temperature

compensated time to rupture

for conventional T/P22

Creep: Temperature

compensated time to rupture

and model prediction for P91

Creep strain and creep to rupture

Experimental evaluation: Multiaxial creep (notched

bar), impression creep, small punch

Creep strain and creep to rupture modelling

In-house LCSP creep strain model

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Utilization of creep models for case studies (Steam mixer 600°C / 100 000 h)

Multiaxial strain

LIFE !

Uniaxial creep models:

rupture, strain, cyclic loading

10

100

1000

10 100 1000 10000 100000 1000000

Time to rupture (h)

Str

es

s (

MP

a)

EPRI raw data

VGB raw data

EN-10216 standard dataManson-Brown model

Wilshire model

EPRI weld data

Multiaxial constraint

FEA

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Service exposure will degrade material and

creep strength to limit life

Gas turbine blades

Boiler tube

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Creep-fatigue testing

Two-way pneumatic loading system (push / pull) based on

bellows technology

Enables creep fatigue crack initiation testing with strain or

stress control, with or without hold periods

The equipment can also be modified for creep-fatigue crack

growth testing

The bellows technology concept is capable of operating in a

range of extreme conditions

High temperature (up to 800ºC)

Pressurized water or steam

Super Critical Water (SCW)

Irradiation environments

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Creep-fatigue assessment for ultra high efficiency pf power plants

Meeting the materials and Manufacturing Challenge for Ultra High Efficiency PF Power Plants with CCS

The concept is to perform innovative demonstrations that will significantly contribute to the EU target to increase the efficiency in existing and new build pulverised coal power plants. This is

necessary as the EC aims to capture and store CO2 to reach a 20% CO2 reduction in 2020.

Demonstration of materials and coatings for boiler and mainstream pipework under Ultra-supercritical (USC) and current steam conditions.

Demonstration of the mechanical integrity of the main steam pipe under USC conditions to a steam temperature of 750°C.

Material testing and evaluation to study creep-fatigue properties of Ni-based superalloys.

Creep-fatigue modelling to support mechanical behaviour extrapolation to actual in-service periods The stress relaxation behaviour assessment and modelling

The creep strain and creep to rupture modelling

The creep-fatigue interaction

Creep-fatigue testing and material properties charazterization Creep-fatigue testing for parent material and cross-weld specimens

A pre-creep exposure of 178MPa / 750°C / 3000h for selected specimens to demonstrate post service simulation

Atlas of fractographs and micrographs

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Creep-fatigue assessment and modelling for nuclear applications

Materials research project for European Gen IV prototypes: the LFR ETPP (European Technology Pilot Plant) Myrrha and the SFR Prototype ASTRID

The modified 9Cr–1Mo (P91) steel is a candidate material for several components of the Generation IV nuclear reactors. Typical in-service conditions require operating temperatures

between 400°C and 600°C, which means that the creep behaviour of these steels is of primary interest. In addition, the repeated start and stop-operations during service lead to

loadings of creep–fatigue type, with very long holding periods in combination with high frequency thermal loads.

Additional qualification experiments to allow codification on P91 material and components

Two-way pneumatic loading system (push / pull) based on bellows technology for creep-fatigue testing

Enables testing in strain or stress control, with or without hold periods

The concept is capable of operating in a range of extreme conditions

High temperature (up to 800ºC)

Pressurised water or steam, Super Critical Water (SCW)

Irradiation environments

Improvement of selected rules and specifying the recommendations on the improved rules (in RCC-MRx, ASME III NH, BS-R5) for creep and creep-fatigue

interaction for P91 components

Creep-fatigue assessment according to methods defined in RCC-MRx, ASME III NH, and BS-R5

Robust models for creep-fatigue life assessment

VTT in-house creep-fatigue model (the Φ-model)

FEA assisted assessment of creep-fatigue rules to P91 components

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