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Project ID: mat193

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PI: Dean PierceCo PI: Govindarajan MuralidharanErcan Cakmak, Larry Allard, Jon Poplawsky, Bruce Pint, Allen Haynes

Oak Ridge National Laboratory

2020 DOE Vehicle Technologies Office Annual Merit ReviewJune 4, 2020

Higher Temperature Heavy-Duty Piston Alloys**Subtask 2A2 under the Powertrain Materials Core Program (PMCP)

2

Program Overview: VTO Powertrain Materials Core Program

Timeline/Budget

• Lab Call Award: July 2018

• Budget: $30M/5 years

• Program Start: Oct 2018

• Program End: Sept 2023

• 30% Complete

Partners

• Program Lead Lab

–Oak Ridge National Lab (ORNL)

• Program Partner Labs

–Pacific Northwest National Lab (PNNL)

–Argonne National Lab (ANL)

Barriers

• Increasing engine power densities & higher efficiency engines; resulting in increasingly extreme materials demands (increased pressure and/or temperature)

• Affordability of advanced engine materials & components

• Accelerating development time of advanced materials

• Scaling new materials technologies to commercialization

FY20 Program Research ThrustsFY20

Budget

Participating

Labs

1. Cost Effective LW High Temp Engine Alloys $1.05M ORNL

2. Cost Effective Higher Temp Engine Alloys $1.525M ORNL, PNNL

3. Additive Manufacturing of Powertrain Alloys $1.075M ORNL

4A. Advanced Characterization $1.025M ORNL, PNNL, ANL

4B. Advanced Computation $0.60M ORNL

5. Exploratory Research: Emerging Technologies $0.75M ORNL, PNNL, ANL

Program structure includes three alloy development thrusts (1-3), a foundational support thrust (4), and a thrust for one-year exploratory projects (5).

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Project Overview: Subtask 2A-2 Higher Temperature Heavy Duty Piston Alloys

Barriers

• Accelerating alloy development time.

• Improving elevated temperature strength

• Maintaining oxidation resistance

• Affordability

• Manufacturability.

Partners

• Subtask 2A2 Lead

–ORNL

• Subtask 2A2 Partners

–Thrust 4

Timeline/Budget

• Subtask 2A2 funding

– FY19: $250k

– FY20: $200k

– Pct. Complete: 30%

Thrust 2: Tasks/Subtasks TRL PI(s) FY19 FY20

Task 2A. Advanced Affordable Wrought Engine Alloys

• 2A1. Oxidation Resistant Valve Alloys (900-950°C)Low/Mid

MuralidharanPint

$400k $400k

• 2A2. High Temperature HD Piston Alloys LowDean PierceMuralidharan

$250k $200k

• 2A3. High Temperature Coatings LowArmstrongDryepondt

$175k $175k

• 2A4. High Temperature Oxidation LowPillai

Haynes$150k $175k

Task 2B. Affordable, High Performance Cast Engine Alloys

-•2B1. Cast Higher Temp Austenitic Alloys LowBrady

Yamamoto$250k $275k

Subtotals $1,225k $1,225k

4

Relevance• Higher cylinder pressures and temperatures = higher efficiency.

• Current heavy duty diesel (HDD) piston steels (4140 & micro alloyed steel (MAS)) not suitable for temperatures >~500oC (low oxidation & fatigue resistance).

• Objective: develop affordable, innovative, higher temperature piston alloys

Exxon Mobil. 2018 outlook for

energy: a view to 2040; 2017

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0

5

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Po

wer

den

sity

(kW

L-1

)

Pea

k C

yli

nd

er P

ress

ure

(M

Pa)

Model Year

Po

wer

den

sity

(H

P L

-1)

80.5

67.1

53.6

40.2

26.8

13.4

Pierce et al., Prog. Mat. Sci. 103 (2019) p. 109).

Bowl rim

Cooling gallery

Ring land Pin boss

0

5

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1995 2005 2015 2025 2035 2045

Worl

d T

ransp

ort

atio

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ner

gy

Co

nsu

mp

tio

n (

Mil

lio

n B

arre

ls p

er

Day

of

Oil

Equiv

alen

t)

Year

Heavy DutyLight DutyAviationMarineRail

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Subtask Targets:

• 4140 and MAS limited to ~500 °C.

– Current industry baseline alloys

– Strength loss above 500°C

– Poor oxidation resistance above 500°C

• New developmental steel targets:

– Operation between 600 & 800°C

– Yield strength: 400 MPa @ ≥600 °C

– Ultimate Tensile Strength: 525 MPa @ ≥600°C

– Cyclic oxidation resistance @ peak temperatures, in air + water vapor

– Long term microstructural stability

– Affordable & manufacturable

Chen et al., SAE Technical Paper Series, 2000-01-1232.

Current commercial heavy duty piston alloys

Heavily oxidized MAS piston with crack

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Milestones2020 Task 2A2: Higher Temperature Heavy-Duty Piston Alloys

Q1 Milestone: Perform testing of mechanical and oxidation properties of different

developmental alloys and down select promising alloy concepts.

Status: COMPLETE, mechanical testing and oxidation testing completed. Down

selected three concept groups.

Q2 Milestone: Fabricate and process optimized alloys for further evaluation

Status: COMPLETE, New optimized alloys have been arc melted and processed.

Q3 Milestone: Evaluate mechanical properties and correlate with microstructure of

optimized alloys.

Status: ON TRACK

Q4 Milestone: Evaluate oxidation and thermal properties of optimized alloys

Status: ON TRACK

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-0.5

0.5

1.5

2.5

3.5

4.5

5.5

6.5

7.5

8.5

9.5

0 100 200 300

Mas

s G

ain

(mg/

cm2

)

Time in 1h cycles

600C air+H2O 1h cycles

4186WS.16412 4226WS.16413

BMN6WS.16414 B946WS.16415

H116WS.16416 T226WS.16417

T916WS.16418

2.25Cr5Cr

9Cr

11-12Cr

Approach:

• Evaluate existing, higher-temperature commercial steels

– Two 12Cr martensitic steels (12Cr-A and 12Cr-B)

• High alloy content = Good performance but high cost

– 4140 (1Cr-1Mn wt.%)

• Evaluate novel, developmental martensitic steels

• Three developmental concepts:

Low cost

Medium cost

High cost

Highest cost

– Low chromium (Cr) alloys (0-3 wt.%): Lowest cost, high strength, 550-600°C.

– Medium Cr alloys (3-8wt.% Cr): Moderate cost, high strength, good oxidation resistance, 600-650°C

– High Cr (8-15 wt.% Cr): Highest cost and oxidation resistance,650-700°C.

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150

250

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450

550

650

750

850

950

1050

1150

0 100 200 300 400 500 600 700

Ult

imate

Tensi

le S

trength

(M

Pa)

Temperature ( C)

12Cr-A12Cr-B4140

As-tempered + aged

500h at 600 C

150

250

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450

550

650

750

850

950

1050

1150

0 100 200 300 400 500 600 700

Ult

imate

Tensi

le S

trength

(M

Pa)

Temperature ( C)

12Cr-A12Cr-B4140

As-tempered

Commercial Alloy Mechanical Property Evaluation

• Commercial 12Cr strength superior to alloy 4140

• 12Cr commercial alloys near targets in as-tempered condition.

• But - strength drops after long term thermal aging

Tec

hn

ica

l A

cc

om

plish

me

nt

525 MPa 525 MPa

Targ

et

Targ

et

4140 data from: Chen et al., SAE Technical Paper Series, 2000-01-1232 and SAE J775 2004-11

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Commercial Alloy Oxidation Evaluation

Break-away iron oxidation at 550C in 12Cr-A After 500h

• Alloy 4140:

– Accelerated oxidation kinetics @500 & 550oC

– Oxide intrusion

– Spallation

Copper plating

Fe oxideCr oxide (not visible

at this mag)

20 µm

4140: 550°C 250h

Oxide intrusion

-0.5

0.5

1.5

2.5

3.5

4.5

0 50 100 150 200 250 300

Mass

Gain

(m

g c

m-2

)

Time (1h cycles)

4140/550 C

4140/500 C

Accelerated kinetics

Oxide spallation

-0.50

0.00

0.50

1.00

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0 100 200 300 400 500 600

Mass

Gain

(m

g c

m-2

)

Time (1h cycles)

12Cr-A/550 C

Break-away

oxidation

12Cr-B/550 C

Tec

hn

ica

l A

cc

om

plish

me

nt

• 12Cr commercial

– 600oC: 12CrA/B optimal slow growing chromia scale

– 550oC: 12Cr-A break-away oxidation

– 550oC: 12Cr-B stable oxidation behavior to 500h

Outer oxide layer

Inner oxide layer

Base metal

50 µm

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• Achieved target strength levels

Low Cost Low Cr alloys Retain Strength at High Temperature

Tec

hn

ica

l A

cc

om

plish

me

nt

450

550

650

750

500 550 600 650 700

Ult

imat

e T

ensi

le S

tren

gth

(M

Pa)

Temperature ( C)

Low Cr B Low Cr DLow Cr E Low Cr FLow Cr G Low Cr H12Cr-A 12Cr-B4140

Target

80 MPa

4140 data from: Chen et al., SAE Technical Paper Series, 2000-01-1232.

Commercial and low Cr developmental alloys: as-

tempered condition

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-0.5

0.5

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2.5

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0 100 200 300

Mas

s G

ain

(m

g cm

-2)

Time (1h cycles)

Low Cr-B

4140

Oxididation Testing at 550 C

• Novel alloying strategies employed

• Lower operating temperatures

• Potential for improved oxidation resistance and strength over 4140 at limited extra cost

Low Cost Low Cr alloys With Improved Oxidation Resistance over 4140

Inner magnetite (Fe3O4) oxide layer

Outer hematite (Fe2O3)oxide layer

Base alloy

Tec

hn

ica

l A

cc

om

plish

me

nt

Low Cr-B alloy250 cycles in air+ 10% water vapor 20 µm

Oxidation Testing at 550 C

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Medium Cr Developmental Alloys Show Exceptional Strength

• Strength targets met in as-tempered condition

• Long term aging to be-conducted

Tec

hn

ica

l A

cc

om

plish

me

nt

Commercial and medium Cr developmental alloys: as-tempered condition

4140 data from: Chen et al., SAE Technical Paper Series, 2000-01-1232 and SAE J775 2004-11

200

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450 550 650

Ult

imat

e T

ensi

le S

tren

gth

(M

Pa)

Temperature ( C)

12Cr-A12Cr-BMed. Cr AMed. Cr BMed. Cr CMed. Cr D4140

Target

140 MPa

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-0.50

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0 100 200 300 400 500

Mass

Gain

(m

g c

m-2

)

Time (1h cycles)

Med. Cr-B

12Cr-B

Med. Cr-C

Med. Cr-D

4140550 C

Med. Cr-A

Medium Cr Developmental Alloys Show Good Oxidation Resistance

• 1st iteration: – exceptional oxidation resistance, low

strength

• 2nd iteration: – Novel alloying to improve strength,

maintain oxidation resistance.

– Med. Cr-A and B: fast kinetics (spallation in A)

– Med. Cr-C and D: slow kinetics (no spall)

– 600 °C testing ongoing

• 3rd iteration underway

Cu coating

Steel

250h @ 600 °C, 1h Cycles, 10%H2O +Air

Oxide layer

Tec

hn

ica

l A

cc

om

plish

me

nt

20 µm

Oxidation Testing at 550 °C

14

Collaborations

Commercial 12Cr-B Tempered 650 °C then aged 500h at 650 °C

• Thrust 4A: Advanced Characterization-ORNL

– Transmission Electron Microscopy & Atom Probe Tomography

– Resulting design knowledge: Large Cr carbides in 12Cr steel provide minimal strengthening

Large Cr carbides

15

Responses to Previous Year Reviewer’s comments

• Project was not reviewed last year

Remaining Challenges and Barriers

• Increase oxidation performance of low and medium Cr alloys while maintaining low cost.

• Further understand mechanisms resulting in improved strength and oxidation resistance in lower cost alloys

• Manufacturability of developmental alloys (melting practice and forgeability)

16

Proposed Future Research

• FY21: – Scale up material to larger sizes to

permit full size test specimens and different types of testing.

– Perform more relevant tests (long term oxidation and elevated temperature fatigue testing) to better simulate engine operation

– Establish collaborations with industry partners to begin addressing barriers to commercialization of new alloys

Any proposed future work is subject to change based on funding levels.

17

Project Summary

Commercial Alloy Evaluation

• Evaluated elevated temperature mechanical and oxidation behavior of commercial martensitic 12Cr steels relative to current piston steels.

• 12Cr commercial steels may offer acceptable strength and oxidation resistance but at high cost.

Medium Cr Developmental Alloy Evaluation

• Novel alloys with improved strength, similar oxidation resistance, and 20-40% lower material cost relative to 12Cr commercial alloys have been developed

Low Cr Developmental Alloy Evaluation

• Low cost low Cr alloys developed with higher strength than commercial 12Cr alloys and good oxidation resistance from 500 to 575°C.

18

Back up slides

19

Technical Backup Slide:Chemical Composition of Current Industry Steels

Composition in wt.% of Steels Currently used in Heavy Duty Diesel Engines

Alloy C Si Mn P S Cr V Ti Mo Fe

MAS 0.34 0.65 1.58 0.01 0.035 0.11 0.09 0.01 - 97.18

4140H 0.47 0.18 1.03 0.027 0.027 0.99 - - 0.2 97.08

Compositions from: Chen et al., SAE Technical Paper Series, 2000-01-1232

20

Technical Backup Slide: Developmental Alloy Cost Summary

• Estimated and normalized raw material cost of developmental alloys relative to 4140

0

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No

rmal

ized

Mat

eria

l C

ost

Alloys

Low Cr Low

Cost AlloysMedium Cr Low

Cost Alloys

12Cr-A

12Cr-B

4140