RECENT ADVANCES IN
CAST SX SUPERALLOYS
Jacqueline Wahl and Ken Harris
®
Cannon-Muskegon® Corporation
A PCC COMPANY
1
Background
• Historically, significant advances in single crystal
alloy performance were attained due to rhenium
effects
• Extensive application of 2nd generation (3% Re)
alloys in the hot section of gas turbine engines
• Consequently, 2nd generation SX superalloys
serve as the benchmark for all subsequent SX
alloy developments
2
New Alloy Developments
• Due to high cost & limited availability of Re, market
pull for improved SX superalloys with low or no Re
compared to 3% Re alloys
• Concurrently, demand for lower fuel burn & reduced
CO2 emissions requires higher temperature
capability beyond 2nd gen. SX alloys, targeting 3rd
generation (6-7% Re) SX alloys
• In response, CM has developed three new,
proprietary SX superalloys:
CMSX®-8 (1.5% Re)
CMSX®-7 (no Re)
CMSX-4® Plus (4.8% Re)
3
CMSX-8 Alloy Development
Alloy Development Goals:
• Excellent high temperature creep-rupture and
LCF properties (targeting 2nd gen. alloy CMSX-4®)
while maintaining
• Oxidation properties/coating adherence
• Castability
• Phase Stability
With significantly reduced Re content
4
CMSX-8 Nominal Chemistry
Alloy
Cr
Co
Mo
Ta
W
Re
Al
Ti
Hf
Ni
CMSX-3
8
5
0.6
6
8
--
5.6
1.0
0.1
Bal
CMSX-7
6
10
0.6
9
9
--
5.7
0.8
0.2
Bal
CMSX-8
5.4
10
0.6
8
8
1.5
5.7
0.7
0.2
Bal
CMSX-4
6.5
9.6
0.6
6.5
6.4
3
5.6
1.0
0.1
Bal
• Re, Ta, Mo, W – balanced for good creep-rupture properties
(with low Re content) and acceptable phase stability
• High Ta content for castability/freedom from freckling
• Cr, Co – adjusted for phase stability
• Al, Ti, Ta – target ~70% Vf γ’ phase
• High Al, low Mo (Ti addition) + Hf addition – improved bare
alloy oxidation/coating adherence
• Density: 8.85 gms/cm3
• DSC Solidus: 1338°C, Liquidus: 1389°C
5
Rupture Life: CMSX-8 vs.
CMSX-4 & Rene’ N5/Rene’ N515
6
Time to 1% Creep
CMSX-8 vs. CMSX-4
7
CMSX-8 Elevated Temperature
Stress-Rupture
8
CMSX-8 Post-test Microstructure
Excellent phase stability/ negligible TCP
phase formation following 4060 hours
stress-rupture testing at 1121°C (2050°F)
9
Alloy Modifications
• CMSX-8 [B/C] alloy
• Modified chemistry w/optimized additions of C, B
• Targeting improved low angle boundary (LAB)
grain defect accommodation for difficult to cast
(e.g., SX vane segments) and/or large industrial
gas turbine components
• Alloy property characterization shows creeprupture results consistent with standard CMSX-8
properties
10
Rupture Life CMSX-8 [B/C] vs.
CMSX-4 & Rene’ N5/Rene’ N515
11
CMSX-8 [B/C] Defect Tolerance
Defect tolerance assessed
on transverse specimens
machined across intentional
LAB/HAB sefects in seeded
bi-crystal slabs
12
CMSX-7 Alloy Development
Alloy Development Goals:
• Improved mechanical properties over existing
non Re-bearing SX alloys
Balanced with
• Good solution heat treatment window
• Castability
• Phase Stability
• Improved oxidation properties/coating adherence
13
CMSX-7 Nominal Chemistry
Alloy
Cr
Co
Mo
Ta
W
Re
Al
Ti
Hf
Ni
CMSX-3
8
5
0.6
6
8
--
5.6
1.0
0.1
Bal
CMSX-7
6
10
0.6
9
9
--
5.7
0.8
0.2
Bal
CMSX-8
5.4
10
0.6
8
8
1.5
5.7
0.7
0.2
Bal
CMSX-4
6.5
9.6
0.6
6.5
6.4
3
5.6
1.0
0.1
Bal
Ta, Mo, W – balanced for improved creep-rupture properties
High Ta content for castability/freedom from freckling
Cr, Co – adjusted for phase stability
Al, Ti, Ta – target ~70% Vf γ’ phase
High Al, low Mo (+ Ti) + Hf addition – improved bare alloy
oxidation/coating adherence
• Density: 8.8 gms/cm3
• DSC Solidus: 1325°C, Liquidus: 1381°C
•
•
•
•
•
14
Rupture Life CMSX-7 vs. CMSX-2/3
15
Time to 1% Creep
16
Rupture Life CMSX-7 vs.
CMSX-4 & Rene N5/Rene’ N515
17
CMSX-7 Post-test Microstructure
Excellent phase stability/ minimal TCP
phase formation following 1176 hours
stress-rupture testing at 1093°C (2000°F)
18
CMSX-4® Plus Alloy Development
Alloy Development Goals:
• Improved high temperature properties over
CMSX-4 alloy, approaching 3rd generation SX
(6-7% Re) alloys, but better all round properties
considering:
• Improved solution heat treatment capability
• No SRZ phase problems/coating compatibility
issues
• Improved oxidation/hot corrosion properties
• Lower Re content, cost & density
19
CMSX-4® Plus Nominal Chemistry
Alloy
Cr
Co
Mo
Ta
W
Cb
(Nb)
Re
Al
Ti
Hf
Ni
CMSX-8
5.4
10
0.6
8
8
--
1.5
5.7
0.7
0.2
Bal
CMSX-4
6.5
9.6
0.6
6.5
6.4
--
3
5.6
1.0
0.1
Bal
CMSX-4 Plus
3.5
10
0.6
8
6
--
4.8
5.7
0.85
0.1
Bal
2
3
0.4
8
5
0.1
6
5.7
0.2
0.03 Bal
CMSX-10K
• Re increased for improved creep-rupture properties,
balanced against adverse effects of SRZ phase & TCP
phase formation
• High Ta content for castability/freedom from freckling
• Cr - adjusted for phase stability
• Ti increased for γ/γ’ mismatch & interfacial chemistry
• High Al, low Mo (+ Ti) + Hf addition – improved bare alloy
oxidation/coating adherence
• Density: 8.927 gms/cm3
• DSC Solidus: 1351°C, Liquidus: 1406°C
20
CMSX-4 Plus Rupture Life
Comparison (hours)
Test Parameters
CMSX-4 Plus
CMSX-4
CMSX-8
517 MPa/913°C
(75 ksi/1675°F)
216
52
67
248MPa/982°C
(36 ksi/1800°F)
615
275
236
296 MPa/982°C
(43 ksi/1800°F)
276
88
89
248 MPa/1010°C
36 ksi/1850°F)
227
82
85
190 MPa/1050°C
(27.6 ksi/1922°F)
231
90
81
103 MPa/1121°C
(15 ksi/2050°F)
662
640
293
21
Time to 1% & 2% Creep
Test Parameters
CMSX4 Plus
CMSX-4
CMSX-8
1%
creep
2%
creep
1%
creep
2%
creep
1%
2%
creep creep
248 MPa/982°C
(36 ksi/1800°F)
374
416
125
160
116
296 MPa/982°C
(43 ksi/1800°F)
171
248 MPa/1010°C
(36 ksi/1850°F)
130
147
35
45
40
48
190 MPa/1050°C
(27.6 ksi/1922°F)
118
138
37
54
34
43
45
136
39
22
CMSX-4 Plus Post-test Microstructure
Excellent phase stability/minimal TCP phase formation
following 1492 hours creep-rupture testing at 1050°C (1922°F)
23
Re Effect (A. Giamei
SUPERALLOYS 2012)
Suggests linear relationship
with increasing Re
24
Re / Alloying Effects
CMSX® …. 8% Ta Alloys
36.0 ksi/1800°F (001)
(248 MPa/982°C)
500
450
CMSX-4® PLUS
MOD C
400
Time to 2.0% Creep (hrs)
350
CMSX-4 PLUS
MOD B
300
250
Suggests
exponential
relationship with
increasing Re
CMSX-4® PLUS
MOD A
200
• [CMSX-4® (6.5% Ta) ]
150
CMSX®-8
100
50
0
1
2
Re wt %
3
4
5
6
CMSX-4 Plus vs. CMSX-10K
Test Parameters
Alloy
Time to
Rupture
Time to
1% creep
Time to
2% creep
248 MPa/982°C
(36 ksi/1800°F)
CMSX-4 Plus
615
374
416
CMSX-10K
718
390
459
103 MPa/1121°C
(15 ksi/2050°F)
CMSX-4 Plus
662
--
--
CMSX-10K
558
--
--
Alloy
Density (RT) kg/dm3
AM1
8.59
CMSX-4
8.70
SC180
8.84
CMSX-4 Plus
8.927
PWA 1484
8.95
Rene’ N-6
8.97
CMSX-10K
9.05
(not density corrected)
26
CMSX-4 Plus Mod C performances under nonisothermal creep conditions
J. Cormier
Institut Pprime, UPR CNRS 3346, ENSMA
1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil
France
27
Webex ANR VISCANOPOL
CMSX-4 Plus Mod C vs CMSX-
27
1. Materials and Specimen
For CMSX-4 Plus Mod C: CM Std heat treatment (Solution + Agings)
For CMSX-10K: RR Solution treatment + GFQ + Agings = 6h/1152 C/AQ + 24h/871
C/AQ + 30h/760 C/AQ
For CMSX-4: CM recommended ST and aging heat treatments
Mechanical polishing of the surface up to a SiC 4000 grade finish (longitudinal
polishing)
CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
2. Tests
Creep under thermal cycling conditions under 120 MPa : 15 min/1050 C + 1 min/1100 C + 15 min/1050 C + 1 min/1150 C.
-1
-1
Heating/cooling rates : 2 C.s /10 C.s respectively
1’/1150 C
T (°C)
1’/1100 C
15’/1050 C
15’/1050 C
Temps
[Cormier et al. Phil. Mag. Let. 2010]
CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
2/2. Creep under thermal cycling – CMSX-4 Plus Mod C vs other SXs
25
CMSX-4 CM1
CMSX-4 CM2
20
Creep strain (%)
CMSX-4 CM3
CMSX-4 DB1
15
CMSX-10K K2
CMSX10K PCC1
10
CMSX10K PCC2
CMSX-4 Plus Mod C #1
5
CMSX-4 Plus Mod C #2
0
0
50
100
150
Time (h)
CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
200
250
300
2/2. Creep under thermal cycling – CMSX-4 Plus Mod C vs other SXs
CMSX-4 CM1
4,5
CMSX-4 CM2
CMSX-4 CM3
Creep strain (%)
3,5
CMSX-4 DB1
2,5
CMSX-10K K2
CMSX10K PCC1
1,5
CMSX10K PCC2
CMSX-4 Plus Mod C #1
0,5
CMSX-4 Plus Mod C #2
0
5
10
15
20
25
30
-0,5
Time (h)
CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
35
40
45
50
3. Microstructure observations (’ in dark)
CMSX-4 Plus Mod C
CMSX-10K
General aspect
CMSX-4
5 mm away from
the failur surface
1 mm away from
the failur surface

A higher ’ volume fraction for CMSX-10K and CMSX-4 Plus Mod C
compared to CMSX-4 (in agreement with the ’ solvus temperature)
CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
7
2/5. Non isothermal creep performance (Number of thermal cycles up to failure)
1000
Mar-M200
René N4
MC2
Y scale logarithmic
AM3
AM1
Cycles to failure
100
René N5
CMSX-4
CMSX-10K
MCNG
CMSX-4 Plus Mod C
10
Very high temperature non-isothermal creep properties controlled by
the ’ solvus temperature
1
1190
1210
1230
1250
1270
1290
' solvus temperature (°C)
CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
1310
1330
1350
1370
Summary/Conclusions
•
Single crystal alloy requirements for new engine
applications take into consideration both operating
conditions and market economy
•
Newly developed SX superalloys offer improved properties
at reduced Re content:
– CMSX-8 similar to CMSX-4 to at least 1010°C (1850°F)
– CMSX-7 exceeds CMSX-2/3 to ~ 1038°C (1900°F) & similar to
Rene’ N5/Rene’ N515 published data
– CMSX-4 Plus approaches CMSX-10K properties
•
These alloys demonstrate improved capability developed
with ~35 years of SX alloy/casting industrial experience
34