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 2 nd generation (3% Re) alloys in the hot section of gas turbine engines Consequently, 2 nd 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 CO 2 emissions requires higher temperature capability beyond 2 nd gen. SX alloys, targeting 3 rd 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 2 nd 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% V f γ phase High Al, low Mo (Ti addition) + Hf addition improved bare alloy oxidation/coating adherence Density: 8.85 gms/cm 3 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% V f γ phase High Al, low Mo (+ Ti) + Hf addition improved bare alloy oxidation/coating adherence Density: 8.8 gms/cm 3 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 3 rd 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 Re Al Ti Hf Ni (Nb) 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 CMSX-10K 2 3 0.4 8 5 0.1 6 5.7 0.2 0.03 Bal 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/cm 3 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 216 52 67 (75 ksi/1675 F) 248MPa/982 C 615 275 236 (36 ksi/1800 F) 296 MPa/982 C 276 88 89 (43 ksi/1800 F) 248 MPa/1010 C 227 82 85 36 ksi/1850 F) 190 MPa/1050 C 231 90 81 (27.6 ksi/1922 F) 103 MPa/1121 C (15 ksi/2050 F) 662 640 293 21
Time to 1% & 2% Creep Test Parameters CMSX4 Plus CMSX-4 CMSX-8 248 MPa/982 C (36 ksi/1800 F) 296 MPa/982 C (43 ksi/1800 F) 248 MPa/1010 C (36 ksi/1850 F) 190 MPa/1050 C (27.6 ksi/1922 F) 1% creep 2% creep 1% creep 2% creep 1% creep 2% creep 374 416 125 160 116 136 171 45 39 130 147 35 45 40 48 118 138 37 54 34 43 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 500 CMSX. 8% Ta Alloys 36.0 ksi/1800 F (001) (248 MPa/982 C) 450 400 CMSX-4 PLUS MOD C 350 Time to 2.0% Creep (hrs) 300 250 200 150 CMSX-4 PLUS MOD B CMSX-4 PLUS MOD A [CMSX-4 (6.5% Ta) ] Suggests exponential relationship with increasing Re CMSX -8 100 50 0 1 2 3 4 5 6 Re wt %
CMSX-4 Plus vs. CMSX-10K Test Parameters Alloy Time to Rupture 248 MPa/982 C (36 ksi/1800 F) 103 MPa/1121 C (15 ksi/2050 F) Time to 1% creep Time to 2% creep CMSX-4 Plus 615 374 416 CMSX-10K 718 390 459 CMSX-4 Plus 662 -- -- CMSX-10K 558 -- -- Alloy Density (RT) kg/dm 3 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 Webex ANR VISCANOPOL CMSX-4 Plus Mod C vs CMSX- 27 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. Heating/cooling rates : 2 C.s -1 /10 C.s -1 respectively T ( C) 1 /1150 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 20 CMSX-4 CM2 CMSX-4 CM3 Creep strain (%) 15 10 CMSX-4 DB1 CMSX-10K K2 CMSX10K PCC1 CMSX10K PCC2 5 CMSX-4 Plus Mod C #1 CMSX-4 Plus Mod C #2 0 0 50 100 150 200 250 300 Time (h) 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 4,5 CMSX-4 CM1 CMSX-4 CM2 3,5 CMSX-4 CM3 Creep strain (%) 2,5 1,5 CMSX-4 DB1 CMSX-10K K2 CMSX10K PCC1 CMSX10K PCC2 0,5 CMSX-4 Plus Mod C #1 CMSX-4 Plus Mod C #2-0,5 0 5 10 15 20 25 30 35 40 45 50 Time (h) CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
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 AM3 Y scale logarithmic Cycles to failure 100 10 AM1 René N5 CMSX-4 CMSX-10K MCNG CMSX-4 Plus Mod C Very high temperature non-isothermal creep properties controlled by the solvus temperature 1 1190 1210 1230 1250 1270 1290 1310 1330 1350 1370 ' solvus temperature ( C) CMSX-4 Plus Mod C vs CMSX-10K vs CMSX-4
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