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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).
3
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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50
60
0
5
10
15
20
25
30
35
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
10
15
20
25
30
1995 2005 2015 2025 2035 2045
Worl
d T
ransp
ort
atio
n E
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
5
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
6
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.
8
150
250
350
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
350
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
9
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
1.50
2.00
2.50
3.00
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
10
• 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
11
-0.5
0.5
1.5
2.5
3.5
4.5
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
12
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
300
400
500
600
700
800
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
13
-0.50
0.50
1.50
2.50
3.50
4.50
5.50
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
0.5
1
1.5
2
2.5
3
3.5
No
rmal
ized
Mat
eria
l C
ost
Alloys
Low Cr Low
Cost AlloysMedium Cr Low
Cost Alloys
12Cr-A
12Cr-B
4140
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