An Accelerated Creep Testing (ACT) Program for Advanced Creep Resistant Alloys for High

Temperature Fossil Energy (FE) ApplicationsAmanda C. Haynes, Dulce Zamorano, Robert Mach, Jack F. Chessa, Calvin M. Stewart

Department of Mechanical, University of Texas El Paso, Texas, Tx 79902

• To increase the efficiency and longevity offossil energy (FE) power plants, advancedultrasupercritical (A-USC) power plants arebeing implemented;

• The A-USC power plants operate for over10,000 hours at pressures above 4000 psi andtemperatures above 1400°F;

• The materials used in these power plantsrequire qualification to withstand theseconditions using accelerated creep testing(ACT).

AcknowledgementDepartment of Energy

National Energy Technology Laboratory

Award number: DE-FE0030331

2. Systematic Approach to SIM and SSM

5. Acceleration Software

1. Motivation

Table 1 - Material qualification procedure using Accelerated Creep

Testing (ACT)

Procedure Advantages Disadvantage

Conventional Creep

Test (CCT)

Creep measurements

occur at constant

stress (in practice

constant load) with

standard or small

punch specimen

• Traditional

• Full Creep

Deformation

Curve

• Rupture Life

• Simple

Equipment

• Destructive

• Large Strains

• Long Times

• Fracture

Processes

• Major State

Changes

Stepped IsoStress

Method (SSM) and

Stepped

IsoThermal Method

(SIM)

Creep measurements

occur at constant

stress that is stepped

increased after a

fixed interval

• Short Times

• Full Creep

Deformation

Curve

• Rupture Curve

• Destructive

• Large Strains

• Fracture

Processes

• Major State

Changes

• Sensitive to

Regression

Analysis

• Advanced

Equipment

Stress Relaxation

Approach (SRT)

Relaxation

measurements occur

at constant strain

(sometimes constant

displacement) near

the elastic limit

• Multiple

Isotherms of

Data

• Creep Activation

Energy

• Non-Destructive

• Small Strain

• Short Times

• No Fracture

Processes

• Nearly Constant

State

• Sensitive to Data

Resolution

• Sensitive to

Numerical

Integration

Scheme

• Does Not

Provide

Full Creep

Deformation

Curves

• Does Not

Provide

Rupture

• Advanced

Equipment

3. Test Setup

(a) Total Strain-Time Data, (b) Creep Strain Adjustment, (c) Extrapolation to Zero Strain, (d) Virtual Start Time Adjustment, (e) Reference – Calibration, (f) Self – Calibration, (g) Accelerated Creep Curve

The Research Objective (RO) of this project is to vet, improve, and test the feasibility of the SIM and SSM accelerated creep tests for metallic materials.

Time

Cre

ep S

trai

n

(b)

cr elastic thermal comp slip cr

t

00 0,T

1 1,T2 2,T

Time

Cre

ep S

trai

n

(c) t0t 0t0

cr

0 0,T1 1,T

2 2,T

Virtual Time

Cre

ep S

trai

n

(d)

0

cr

1 1,T2 2,T

0t t

0 0,T

Cre

ep S

trai

n

(e)

12

CCT Reference0

* 00 0log , , , ,i

i i i i

i

t tf T T t

0

Time t

cr

Reference-Calibration of SSM

Accelerated Time

Cre

ep S

trai

n

(g)

1

2

t

Accelerated Creep Curve

0

cr 0

Initial Horizontal and Vertical Adjustments

4. Test Matrix

Conventional Creep Tests (CCTs)

Time

Cre

ep

Str

ain

(a)

cr

t

0 c

0T

1T

2T3T

Reference Stress

Time

Cre

ep

Str

ain

(b)

cr

t

0T c

0

1

23

Reference Temperature

Accelerated Time

Cre

ep

Str

ain

(c)

cr

log / it

0 c

0T c

0 0log , , ,i i if T T

Unified Master Curve

SSM Acceleration SoftwareExperimental Data File

Run

Global Inputs

# of Stress Steps

Initial Stress

Stress Increment

Temperature

Save Exit

Time

Str

ain

(a)

Str

ess

0 0,T1 1,T

2 2,T

*

rt

tt c

Cre

ep S

trai

n

(f)

1

2

00

Log10 Time log t

cr

Self-Calibration of SSM

0

, , 1E i S i

, , 1E i S i

300,000 hoursCreep-Rupture of 9Cr-1Mo Tube

Uncertainty ↑Temperature ↑

Stress ↓

MERG HT DIC System

Furnace

450nm

Bandpass

filter

Camera

450nm

Spotlight

A.

Unfiltered

Room

Tem

p

C.

450 nmR

oom

Tem

p

Time

Cre

ep

Str

ain

(d)

cr

t

0 c

0T c

Time, t (hours)

0 20 40 60 80 100 120 140 160 180

Cre

ep S

train

,

cr (m

m/m

m)

0.000

0.005

0.010

0.015

0.020

0.025

0.030

CCT Reference

SSM MPa

600°CMPa

Time, t (hr)

0 20 40 60 80 100 120 140 160

Cre

ep S

trai

n,

cr (

%)

0

1

2

3

4

5

6

7

8

9

10

300 MPa

320 MPa

600°C

304 SS Preliminary ACT Test

Test 2 – Test-parameter decision matrix for SIM and SSM

SIM Maximize Acceleration?

0

0 set to the design stress.

0T

0T set to the design temperature.

0T 0 3TT T T where TT is the temperature of the next mechanism transition. t 0t minimizes real time thus maximizes the acceleration.

SSM Maximize Acceleration?

0

0 set to the design stress.

0 0 3TT T where T is the stress of the next mechanism transition.

0T

0T set to the design temperature.

t 0t minimizes real time thus maximizes the acceleration.

Can we capture this uncertainty in an accelerated manner?

50kN · 1200 C

Gas Port

Qu

art

z V

iew

Po

rt

Instron 5969 (50kN capacity)

ATS Series 3120 Split Tube Furnace Ambient up to 1200 C with Watlow PM

Epsilon Model 3549 Mountable High Temperature Extensometer

Equipment for SSM

Subroutine 1:

Data Processing

Subroutine 2:

Calibrate McVetty’s

Law for each step

Subroutine 3:

Calibrate Time Factors

Subroutine 4:

Data Acceleration and

Generate Deformation

Curve

Subroutine 5:

Output Results and

Error Analysis

High Temperature DIC with Ultraviolet (UV)

Light

Mock User Interface for the ACT Software

Matlab Code Flow Chart

Time

Cre

ep S

trai

n

cr

t

Time-Temperature-Stress Superposition

(a)

(b)

(c)

(d)

SSM or SIMCCT

1 1,T2 2,T