ICME Design of Ni & Co Superalloys - QuesTek · PDF fileTensile Test Results (ASTM E8 and E21) ... • Heat treatment optimization ... - CW not required for strength Wear - Low CoF

ICME Design of Ni & Co Superalloys

Jiadong Gong

QuesTek Innovations LLC

March, 2016

Rev - 2016

p. 2

Jiadong Gong


SRG 2016 - March, 2016

QuesTek’s ICME approach

• Systems-based design approach utilizing computational tools to model key process-

structure and structure-property linkages

• Replacing the legacy trial-and-error approaches with parametric materials design• Faster, cheaper, targeted material performance

Modeling at all length-scales relevant to materials

design and processing

Treat material as a system, linking process-

structure-properties to meet defined performance

goals

p. 3

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SRG 2016 - March, 2016

ICME Design of Ni Superalloy

p. 4

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SRG 2016 - March, 2016

DOE SBIR: Single Crystal (SX) Ni Superalloy for IGT

• DOE SBIR Phase I, Phase II, and Phase IIA award

• SX castings – High Temperature Performance– Desirable for better creep resistance – no grain boundaries

• IGT blade castings are large > 8 inches– Slower solidification / cooling rates exacerbate processing issues

• Primary casting (processing) constraints:– Freckle formation

– High angle boundaries (HAB) and low-angle boundaries (LAB)

– Hot-tearing

– Shrinkage porosity

• 3rd generation blade alloys are especially difficult to cast

as SX due to their high refractory content– Increased tendency for hot tearing

– Increased tendency for freckle formation

QuesTek’s proposed approach: ICME-based design of a new processable, high-

performance single crystal alloy for IGT applications

p. 5

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SRG 2016 - March, 2016

List of benchmark alloys

ID Re Al Co Cr Hf Mo Ta Ti W other

PWA1480 - 5 5 10 - - 12 1.5 4

PWA1483 - 3.6 9 12.2 - 1.9 5 4.1 3.8 0.07C

GTD444 - 4.2 7.5 9.8 0.15 1.5 4.8 3.5 6 0.08C

CMSX7 - 5.7 10 6 0.2 0.6 9 0.8 9

CMSX8 1.5 5.7 10 5.4 0.2 0.6 8 0.7 8

PWA1484 3 5.6 10 5 0.1 2 9 - 6

CMSX4 3 5.6 9 6.5 0.1 0.6 6.5 1 6

Rene N5 3 6.2 7.5 7 0.15 1.5 6.5 - 5 0.01Y

CMSX10 6 5.7 3 2 0.03 0.4 8 0.2 5 0.1Nb

TMS238 6.4 5.9 6.5 4.6 0.1 1.1 7.6 - 4 5.0Ru

QuesTek’s Phase I design (“QT-SX”) contained these same

elemental constituents, but with 1% Re

Re-free

alloys

Recently-

developed

2nd Gen alloys

High-Re alloys

p. 6

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SRG 2016 - March, 2016

Systems design chart for SX castings

p. 7

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SRG 2016 - March, 2016

Modeling of liquid density during solidification

7.615

7.620

7.625

7.630

7.635

7.640

7.645

7.650

1,320 1,330 1,340 1,350 1,360 1,370 1,380 1,390 1,400 1,410 1,420

ReneN5 Liquid density vs. T

40%

20%

liquid

density,

g/c

m3

Temperature, °C

liquidus

Actual modeling

output is a

combined use of

various databases

and software

Freckle-resistance is related to the modeling of the liquid density during

solidification base on a critical Rayleigh number:

p. 8

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SRG 2016 - March, 2016

Modeling freckling behavior in N5 and QT-SX castings

Target this range (>B, <A)

p. 9

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SRG 2016 - March, 2016

0

0.005

0.01

0.015

0.02

0.025

0.03

(a): Liquid density difference at 20% solidification

0.00E+00

2.00E-20

4.00E-20

6.00E-20

8.00E-20

1.00E-19

1.20E-19

1.40E-19

(b): Coarsening Rate Constant for different alloys

Coarsen rate and liquid density difference comparisons

Comparable coarsening rate

to CMSX-8 (1.5% Re) alloy

Reduced buoyancy

differences (less than

non-Re CMSX-7)

(lower is better)

1%

Re

3%

Re0%

Re1%

Re

0%

Re

1.5%

Re

p. 10

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SRG 2016 - March, 2016

2nd round of casting results

p. 11

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SRG 2016 - March, 2016

As-cast Microstructures

QT-SX

ReneN5

Along growth direction Transverse

p. 12

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SRG 2016 - March, 2016

Microstructure after double-step aging

Characterization and microstructure analysis confirm the achievement of the design goal of γ’ phase fraction and lattice misfit

(no evidence of TCP phases were found during all heat treatments)

p. 13

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SRG 2016 - March, 2016

Atom-probe (LEAP) analysis of the QT-SX nanostructure

Ion, at.% Cr % Ni % Co % Al % Hf % Mo % Re % Ta % Ti % W %

LEAP1 1.74 66.76 6.63 17.28 0.05 0.61 0.10 3.43 0.38 2.84

LEAP2 1.92 70.34 6.64 16.97 0.08 0.85 0.07 0.72 0.42 1.79

Prediction 2.1 69.0 6.0 16.9 0.05 0.23 <0.01 4.0 0.19 1.6

γ'

γ

γ'

γ'

γ

γ'

γ'γ'

Excellent agreement

with predicted

compositions (γ’

comparisons below)

p. 14

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SRG 2016 - March, 2016

Performance at elevated temperature

Evolution of microstructures during long-term exposure at elevated temperature

Tensile Test Results

(ASTM E8 and E21)

Comparison to Select

Incumbent SX alloys*:

*Baseline data taken from

respective patent filings

p. 15

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SRG 2016 - March, 2016

Stress Rupture Test Results (ASTM E139)

Comparison to Select Incumbent SX alloys*

*Baseline data taken from respective patent filings, literature

p. 16

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SRG 2016 - March, 2016

In Process

• Full blade casting trials

• Heat treatment optimization

• Extended characterization

• Long-term thermal stability

• Long-term performance evaluation

• Coating compatibility

• Continuing Phase IIA

• Additional full blade castings

• Commercialization & Test matrix

p. 17

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SRG 2016 - March, 2016

ICME Design of Co Superalloy

p. 18

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SRG 2016 - March, 2016

Technical Background

A high-strength, wear-resistant material alternative to CuBe is sought

for highly loaded, unlubricated aerospace bushing applications to

avoid health-hazards associated with Be.

• Key property goals are WEAR resistance and STRENGTH

• Low-friction bushing applications

• Achieve strength in large product sizes without cold work (Quench suppressibility)

Objective:Design and develop an environmentally safe drop-in alternative alloy as a

substitution for highly loaded bushing applications.

Vertical Tail Hinge Assembly

Wing Lug Attach

Main Landing Gear

p. 19

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SRG 2016 - March, 2016

VIM/VAR

melting

Homogen-

ization

Hot working

>4” dia.

Solution

treatment

Machining

Tempering

Processing Structure

Solidification

structure

- Inclusions

- Eutectic

Grain Structure

- Grain size

- GB chemistry

- pinning particles

- Avoid cellular

reaction

Nanostructure

- Low-misfit L12

- Size & fraction

- Avoid embrittling

phases

Matrix

- FCC (avoid HCP

transformation)

- Low SFE

- Solid solution

strengthening

Properties

Non-toxic

Strength

-120 to 180 ksi

compressive YS

- CW not required

for strength

Wear

- Low CoF

- Galling/fretting

resistance

Toughness

-Highly ductile

after solution treat

- High toughness

fully hardened

Corrosion

Resistant

Environmentally

Friendly

Bearing Strength

Wear Resistance

Damage Tolerant

Formable

Performance

Corrosion

Resistant

Systems Design: L12-strengthened CoCr

p. 20

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SRG 2016 - March, 2016

Co

Al

W Co

Ti

Cr

Co System Thermodynamics with L12 γ’

Iso-section at 1173K

● Develop thermodynamic database● Search composition space for achieve targeted microstructure

● Co-Cr-Ti-W-Fe-Ni-V-C multicomponent thermodynamic database assessment complete

● Design for FCC – L12 lattice parameter matching for stable, coherent

dispersion● Avoid cellular growth reactions at grain boundary (Cr, Fe & V to reduce misfit)

● Stabilize FCC (vs. HCP) at tempering temperature (Fe, Ni)

γ’

γ’

p. 21

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SRG 2016 - March, 2016

Validation of Design with LEAP

Matrix

Precipitate is enhanced in

Co, Ti;

slightly enhanced in Ni, V

Matrix is enhanced

in Fe, Cr

Precipitate

Matrix

Precipitate is enhanced in

Co, Ti;

slightly enhanced in Ni, V

Matrix is enhanced

in Fe, Cr

Precipitate

Validation of alloy nanostructure

using atom probe tomography after

tempering at ~780 °C:

FCC (Co-rich) matrix and γ’ (L12

crystal structure, Co3Ti-type)

strengthening nano-precipitates

Side view

Top view

Co

Cr

Ti

Ni

Fe

p. 22

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SRG 2016 - March, 2016

Tempered condition for 1st Generation characterization(aged at 780C/24 hours – Hardness of 34.8 HRC)

410 HV

Scale-up Production and Process Optimization

Alloy production (500 lb. VIM/VAR scale)

Heat treatment optimization is

performed by isothermal holding at

different aging temperatures for

various times (note long times).

The peak hardness condition is identified

as 780 °C for 72 hours

T = 780 °C

after forging

p. 23

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SRG 2016 - March, 2016

QuesTek Cobalt Alloy Property Comparison

Room Temperature Tensile Property

QuesTek Cobalt*

Haynes 188(AMS 6508 Sheet)

Haynes 25(Hot-rolled +

Annealed Bar)

Haynes 556™(Hot-rolled +

Annealed plate)

Ultimet®(Solution

Treated Bar)

Stellite 6®(Investment

Cast)

Tensile Strength 200 ksi 137 ksi 147 ksi 116 ksi 147 ksi 115 ksi

0.2% Yield Strength

127 ksi 67 ksi 73 ksi 55 ksi 76 ksi 96 ksi

Elongation 33% 53% 60% 51% 38% 3%

Reduction in Area 28% - - - - 3%

Hardness, RC 38 30 41

• Designed for low-friction bushing applications as an alternative to high-strength

CuBe alloys

• The new design has demonstrated better wear resistance in pin-on-disk and

reciprocating wear tests, compared to baseline AMS4533 CuBe alloy.

• Additional interest from turbine engine OEMs

• QuesTek patent pending

* Based on initial evaluations of 2” round hot forged bar, solution treated and aged at 780°C, produced at 500 lb. VIM + VAR scale

p. 24

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SRG 2016 - March, 2016

Further Testing

• Better fatigue

• Better friction

• Better galling

• Sub-scale bushing

p. 25

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SRG 2016 - March, 2016

Latest Progress

• New alloy production

• Recent modeling

• Mobility database updates

• Temper optimization

• AIM Qualification

• New Air Force SBIR Phase I

• Alternative Materials to Cu-Be for Landing Gear Bushing/Bearing Applications

p. 26

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SRG 2016 - March, 2016

Summary

• Thermodynamic and process modeling ICME tools have been applied to

the design of L12 precipitate-strengthened high-strength wear-resistant

Co-base alloy

• A full-scale prototype has been produced and extensive performance

testing shows excellent properties and high potential for the alloy as a

CuBe replacement

Continuing Activities at CHiMaD

• Extension of Co CALPHAD thermodynamic and kinetic databases

• Calibration of strength model to prototype data

• Prediction of multi-step temper to reduce time to peak strength

• High temperature application exploration

p. 27

Jiadong Gong


SRG 2016 - March, 2016

Thank you!

For more information, contact:

Jiadong Gong

Senior Materials Design Engineer

QuesTek Innovations

847.425.8221

[email protected]

www.questek.com

p. 28

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SRG 2016 - March, 2016

p. 29

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SRG 2016 - March, 2016

(left) Setup of the small scale test slab cluster (right) Picture of actual casting with N5 showing a bi-grain formation

Simulation of chosen casting scenario with N5: (a) R contour (b) G contour (c) location designations

One “tree” (four

castings) produced by

PCC from both N5 and

QT-SX

1st round of casting results

p. 30

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SRG 2016 - March, 2016

2nd round of casting results

p. 31

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SRG 2016 - March, 2016

Oxidation modeling

Oxygen concentration computed at

FCC/Oxide* boundary assumed to be the

content in FCC when the spinel forms

• Both Al2O3 and Cr2O3 expected to form at high T

• Internal Al2O3 expected to form below 850°C

Model agrees well with experimental data for benchmark alloys

• Continuous Al2O3 and Cr2O3 formation

• Wahl applied Wagner’s model to multicomponent systems

𝑦𝑀0 ≥ 𝑦𝑀𝐶1

0 =𝜋𝑔

2𝜈𝑁𝑜

𝐷𝑂𝑉𝐴𝑙𝑙𝑜𝑦𝐷𝑀𝑉𝑀𝑂

1/2

p. 32

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SRG 2016 - March, 2016

Oxide characterization

EDS mapping of continuous oxide in QTSX alloy heat treated for 100h at 1000°C.

Continuous Al-rich oxide observed in all samples

QTSX oxidized in air for 100h at 900°C, 1000°C and 1100°C

p. 33

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SRG 2016 - March, 2016

QuesTek Creep Modeling

• γ’ Coarsening Rate Constant

• Reed creep merit index: Assumes that the diffusivity at the γ/γ’ interface

controls the climb process = rate controlling mechanism during creep

Alloy Creep merit index (m-2 s *1015) Coarsen KMP*1020

CMSX-10 6.93 4.59

PWA1484 5.68 5.97

CMSX-4 4.51 6.00

QTSX 3.97 6.59

René N5 3.82 7.17

TMS238 3.47 4.94

PWA1483 2.77 12.2

Re free

Re 1 wt.%

Re 3 wt.%

Re 5 ≥ wt.%

QTSX is predicted to have creep behavior similar to alloys containing higher

amount of Re, like the 2nd generation alloys

p. 34

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SRG 2016 - March, 2016

Stress Rupture Test Results (ASTM E139)

Comparison to Select Incumbent SX alloys*

Raw Data

*Baseline data taken from respective

patent filings, literature

IDTest Temperature

(Deg F)

Test Stress

(MPa)Life (hrs)

Elongation

(%)

SR1 1600 551.6 76.7 20.6

SR2 1800 275.8 86.6 30

SR3 1800 241.3 147.4 43.8

SR4 1800 206.8 340.6 41.4

SR5 1900 172.4 224.6 43.8

SR6 2000 137.9 119 30.6

SR7 2100 89.6 107.7 24.8

27

28

29

30

31

32

33

L-M

Para

mete

r [T

(20+

log(t

))/1

000]

L-M Parameter at 150MPa

1%

Re3%

Re

1.5%

Re3%

Re

3%

Re

6%

Re

6.4% Re

5% Ru

0%

Re0%

Re

p. 35

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SRG 2016 - March, 2016

Previous Alternatives to CuBe

Properties of available alternative alloy materials do not meet the full

range of design requirements

p. 36

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SRG 2016 - March, 2016

Design Concept: CoCr alloy with precipitation strengthening

• High Cr content – Wear/Corrosion

• Minimize the hardness and ease of machining in

annealed state– Minimize interstitial elements (C, N)

– Most machining before final solution heat treatment

• Design for a precipitation-strengthening dispersion

– Solution-treatable following (rough) machining in

annealed state

– Efficient precipitation during tempering > ~700-900°C

– Coherent phase is ideal: (L12 or γ’) – Co3Ti

– Similar microstructures demonstrated for CoAlW (Cr-

free) alloy, but we need Cr (SFE)

– Ensure good lattice parameter matching between the

FCC matrix and ordered FCC (L12) particles

• Design for good solidification and hot-working

• Design for an efficient grain pinning dispersion

– TiC/VC can be effective at low phase fraction

J. Sato et al., vol. 312, Science, 2006

p. 37

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SRG 2016 - March, 2016

Lab-scale Proof of Concept

Solidification and Homogenization• Large grains with significant twinning

• No evidence of large particles on the grain boundaries, nor dispersed in the matrix

As-cast

~9% eutectic

Homogenized at 1060°C:

mostly homogenous

p. 38

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SRG 2016 - March, 2016


Temper Study

850 °C /8 hr

850 °C /24 hr

• Annealing twins (evidence of FCC with low SFE)

• No cellular growth (discontinuous precipitation) or unusual grain boundary particles

p. 39

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SRG 2016 - March, 2016


L12 Precipitation Nanostructure

Annealing twin in FCC grain Nano-scale (~100 nm) particles

with cubic orientation to matrix -

evidence of L12 phase

p. 40

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SRG 2016 - March, 2016

Design Iteration:

Optimize Strength and Processability

γ’=16% γ’=22%

1st Gen (NGCO-1A) 3rd Gen (NGCO-3A)

γ γLL

Solution window

CALPHAD step diagrams from QuesTek proprietary database

p. 41

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SRG 2016 - March, 2016

Fatigue Performance Comparison

NGCo-3A Fatigue Life Comparison Shows Superior Performance

p. 42

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SRG 2016 - March, 2016

Galling Performance Comparisons

NGCo-3A has Lower Coefficient of Friction (Better Wear Performance)

NGCo-3A Galling Shows Equivalent Performance to Cu-Be

p. 43

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SRG 2016 - March, 2016

Environmental Bushing Testing Performance

NGCo - 3A• Lower Rotational Load

• Lower Temperature Response

• Equivalent Static Wear Displacement

CuBe• Higher Rotational Load

• Higher Temperature

• Equivalent Static Wear Displacement

NGCo-3A was Superior in Galling Initiation Test Evaluation

Documents

ICME Design of Ni & Co Superalloys - QuesTek · PDF fileTensile Test Results (ASTM E8 and E21) ... • Heat treatment optimization ... - CW not required for strength Wear - Low CoF