CFM HPT Blade - Overview

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February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 1
HPT Blade - Overview
• Blade configuration
• Trailing edge root cracks
• Shank separation
• Airfoil separation
• Trailing edge separations
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2002M52P05
N5
Full Wrap TBC
Improved Film
Cooling
Intro. 1997
-7 Baseline
-5B/P S/B 72-163
2002M52P09/P11/P14
N5
P09 Full Wrap TBC
P11 1/2 Wrap TBC
Platform Cooling
P14 same as P11 with Thinned
Shank Coating
Intro. 1999
-7 S/B 72-115/116
-5B/P S/B 72-271
N5
P11 plus optimized
T/E cooling
Shank
improvements
Production Intro.
4Q 2001
1957M10P01
CFM56 HPT 3D Aero Blade Configurations
2002M52P04
N5
Full Wrap TBC
Intro. 1994
-5B/P Baseline
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HPT Blade
Root Trail Edge Cracks
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HPT Blade Root Trailing Edge Cracks
BACKGROUND
• Early blade design have exhibited root trail edge cracks in service
- 2002M52P04 and P05 HPT blades affected
+ 373 -7B engines delivered with P05 blades
• No CFM56-7 engines delivered with P04 blades
+ 29 -5B/P engines delivered with P04 blades
• 207 -5B/P engines delivered with P05 blades
• No IFSD’s
• 39 UER’s (35 for -5B/P; 4 for -7)
- Detailed borescope inspection effective
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HPT Blade Root Trailing Edge Cracks
2002M52P04/P05
Area of root trailing edge
crack initiation and
propagation
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Reduced Borescope Inspection Program
Proven to be Very Effective
HPT Blade Root Trailing Edge Cracks
• Containment program - borescope inspection
- Focused inspection required for detection
+ Training video produced and distributed to all customers
+ Fleet Highlites articles written to increase awareness
+ Contact CFMI if assistance required with training
• Service Bulletins issued for borescope inspection
- -7B S/B 72-326 -- Issued June 2001
+ 2002M52P05 blade only
- Reduced borescope inspection intervals - every 1000 cycles
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Typical TE Crack Indication
HPT Blade Root Trailing Edge Cracks Borescope
• On-Wing Maintenance Manual Limits for Root Trailing Edge Cracks
- Every 400 cycles if crack is less than 0.120 inch (3,0 mm)
- Every 200 cycles if crack is between 0.120 and 0.200 inch
(3,0 to 5,1 mm)
- 40 cycle over-service extension if crack is between 0.200 and 0.300 inch (5,1 to
7,6 mm)
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HPT Blade Root Trailing Edge Cracks
• Corrective action program
- 2002M52P09 / P11 blade introduced in 1999
+ Factory endurance testing has demonstrated 3X improvement in T/E root
airfoil capability over the P04/P05
- 2002M52P04/P05 blade retirement program at next shop visit
+ -7B S/B 72-115 revised June 2001 - Category 4
• Logistic plan in place
• Special procedure developed to change blades
- ESM 72-00-52, Special Procedure 002
- Shop visit not required in most cases
- Replace all 80 blades without removal of HPT disk using pre-ground,
balanced blades
- December 2001 Fleet Highlites article introduced procedure
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• Further durability improvements - 1957M10P01 HPT blade
- 9000 accelerated development engine cycles…. no visible cracks.
Testing continuing.
• Production introduction (SAC) 888-767, -772, -773, -776, -777, 779, -
780 through -793, -795 and up.
• Production introduction (DAC) 876-757 and up
• HPT blade kit PN 737L325G03 available April 2002
- Kit contains a set of 80 pre ground HPT blade PN 1957M10P01,
balanced and numbered blades
P01 Factory Testing Demonstrating Further Improvement in Trail Edge
Crack Capability
HPT Blade Root Trailing Edge Cracks
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Enhanced HPT Blade P/N 1957M10P01
Reduced row 1 flow
(13 vs. 19 holes)
Extend row 8
to platform
(added 1 hole)
Add 4 holes
to root
Uniform row
8 spacing
Reduced size
trailing edge
slots (0.040 to
0.033”)
Pressure side cooling
near the platform
Major Features same as P11
• N5 Material
• Optimized cooling
• Pt-Al base coat
• TBC on pressure side
Smoothed internal
shank cooling
passage geometry
with same thinned
internal coating as
P14 blade
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CFM56 3D Aero HPT Blade
Shank Separation
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HPT Blade Shank Cracking
• CFM56-5B6/2P IFSD
- November 2000
- Contained
- TSN / CSN = 9027 / 8745
- HPT Blade separated in blade shank
+ HPT Blade PN 2002M52P04
+ One other shank separation due to secondary damage
+ Other blade airfoils separated due to secondary damage
Event Description
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• Only shank separation event to date
- 3100 engines in 5B/P and -7B fleets
- Over 9 million cycles
HPT Blade Shank Cracking
H P T 3D Ae ro F le e t
0
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
10000
10500
C SN
Qty
C FM 5 6 -5B /P
C FM 5 6 -7B
Event
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BACKGROUND
• HPT blade is a single crystal N5 material, with an
aluminide internal coating
- Coating reduces oxidation/corrosion
- Three coating processes used
+ All three coating processes within specification
+ Coating thickness correlates with process
• Coating thickness affects LCF initiation
- Verified via laboratory specimen testing
- Thinner coating better
• Cracking initiated at high stress location
- Cooling cavity transition
HPT Blade Shank Cracking
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Cross Sectional View of Cooling Cavity
Local stress
riser at transition
0.420 inch (10,7 mm)
HPT Blade Shank Cracking
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Metallurgical Investigation
• Initiated at mid-cooling passage
– Initiation / propagation in Low Cycle Fatigue (LCF)
– Transitioned to crystallographic fatigue
– Shank geometry common to all 2002M52P04 through P14 blade part
numbers
Crack
Location
Cross sectional
view of cooling
cavity
Primary blade
Separation
Secondary blade
separation
(Tensile overload)
HPT Blade Shank Cracking
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• Nine engines removed to sample high-cycle blades
- Five CFM56-5B/P (up to 7599 CSN)
- Four CFM56-7B (up to 9050 CSN)
- Two of the three coating processes represented
+ Limited data from second process
+ Blades from third process too young for meaningful data
• Findings
- Approximately 4125 blades inspected
+ Sampling engines plus routine shop visits
+ Visual, eddy current, and metallurgical
- 237 blades have been found with shank cracks
+ All cracked blades from process that yields thickest coating
+ All cracks detected using Eddy Current probe & verified by cut up
Field Investigation
Cracking Not as Severe as Originally Estimated
HPT Blade Shank Cracking
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• Blade Design Changes
• Blade Rework
• Test Program
• Field Recommendations
HPT Blade Shank Cracking
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• Interim action taken:
- PN 2002M52P14 blade released
+ CFM56-5B/P SB 72-0400
• ESN Intro.: 575-233 and up
+ CFM56-7B SB 72-0337
• ESN Intro.: 889-505 and up
• 888-477, -496 through -497, -503 and up
- Thinner internal coating in shank area
• New blade introduced, PN 1957M10P01
- Phased production introduction started in 4th quarter 2001
- Same coating process as P14 blade
- Redesigned internal casting geometry to reduce stress
- Service Bulletin to release to field April 2002
Blade Design Changes
HPT Blade Shank Cracking
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Blade Rework
• CFM has developed strip process for blade coating removal.
Steps:
- Inspect for internal cracking with Eddy Current probe
- Strip process to remove internal coating
- External coating rejuvenation/tip repair
- Re-identify to new part number
• Estimate 2Q02 availability
HPT Blade Shank Cracking
Test Program
• Factory engine test cyclic endurance testing on-going
- Mix of field returned high cycle blades, redesigned blades, reworked blades
- Data to supplement field data
- Completes 2Q02
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Field Recommendations
• No change to current maintenance recommendations
- No on-wing inspection possible (internal coating)
- At SV process per ESM and applicable SB’s
• Update on field findings and metallurgical evaluation to be
provided as data accumulates
- Continue to evaluate blades returned from routine shop visits
- Continue detailed metallurgical evaluations of blades
+ Including data from the other coating processes
• Establish field recommendations based on field returned blade
findings
- Coating process
- Engine model / rating differences
- Data supplemented by factory engine test
HPT Blade Shank Cracking
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CFM56-5BP/-7 HPT Blade
Airfoil Separation
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Events
HPT Blade Airfoil Separations
• Four airfoil separation events, one CFM56-5B/P, three CFM56-7B
- Time, cycle and thrust ratings vary
- All engines were first run
Event date Model ESN Rating TSN CSN Part Number
May 2000 -7B 875-256 B22 5057 3265 2002M52P05
Nov 2000 -7B 874-163 B24 6401 6164 2002M52P05
Feb 2001 -7B 876-561 B26 769 1006 2002M52P11
Jul 2001 -5B/P 779-384 B3 1567 758 2002M52P05
• Events have similar overall characteristics -5B/P -7B
- Airfoils separated just above platform  
- No evidence of abnormal operation  
- No evidence of combustor involvement  
- No source of fatigue stimulus identified  
- No evidence of manufacturing related cause  
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HPT Blade
Airfoil
Separation
Rupture
Tensile overload
LCF
HCF
Potential Root Cause Flowchart
Eliminated
Probability
Potential Separation Mechanisms Scenarios
Low
High
Medium
• Pre existing trail edge root cracks
• Material pedigree
• Coating impact (internal cracks)
• Local stress exceeds material capability
• DOD/FOD
• Loss of cooling flow
• Plugging in blade
• Plugging in inducer
• Loss of retainer sealing
• Material pedigree
• Pre existing cracks/missing material (frequency shift)
• Material pedigree
• Coating impact (internal cracks)
• Loss of damping
• High mean stress
• Vibratory stimulus
• HPT nozzle area
• Combustor profile/pattern
• Fuel staging
• Fuel nozzle flow
• LPT nozzle area
• TBV scheduling
• Secondary flow circuit
HPT Blade Airfoil Separations
Telemetry testing to investigate
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• Telemetry test conducted to measure blade vibratory stress
levels under various engine operating conditions
- 35 of 80 blades instrumented; 5 different gage locations
- Over 25 hours testing completed November ‘01 including 60
transients
- Overall, blade responses similar to previous tests …however:
• One blade had higher than expected response on blade tip gage
after throttle burst to take-off speed conditions
- Response lagged 10-15 seconds after target speed reached
- Would result in high vibratory stress in failure location
- Response not seen on other blades with same gage location
Investigation Status
HPT Blade Airfoil Separations
Unusual blade vibratory response measured in telemetry testing
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• CFMI working to
understand single blade
response
- Telemetry instrumentation
re-validated post-test
- Analysis being conducted
to support single blade
response
- Detailed characterization
of blade (frequencies,
geometry)
- Second build of telemetry
engine likely
Investigation Status
HPT Blade Airfoil Separations
Time Lag
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CFM56-5BP/-7 HPT Blade
Trailing Edge Separation
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6 Events of HPT blades with missing trailing edge material
• Missing HPT blade material observed on factory endurance engine 779-193/4a
• 5 events reported from the field
ESN Blade PN PTSN PCSN
779311 2002M52P05 9025 3968
779318 2002M52P05 7942 5002
779299 2002M52P05 8452 5274
874494 2002M52P09 9403 3249
875240 2002M52P05 10459 3772
Root Cause Identified
• Metallurgical investigation determined that an LCF crack initiated on the
inside wall of passage 8 of the airfoil
• Crack propagated to liberate blade trailing edge material
• Crack initiation was due to a high stress concentration that resulted from a
sharp corner that was machined into the blade core
Trailing Edge Separation
Radial
Crack
Found During Routine BSI, no Reports of indications
Vibration, Minor Downstream Damage
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Trailing Edge Separation
Manufacturing Changes
 Manufacturing process was immediately changed to preserve the low stress core
generated radius in cavity 8
 Parts shipped after January 1999 were produced with the improved manufacturing
process change
 Blades with the manufacturing process change have exceeded 7500 factory endurance
cycles to date without cracks.
Status
• CFMI working to identify affected population through manufacturing records review
• Updates will be provided during routine WTT calls
• No field recommendation at this time
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• Root Trail Edge Cracking
- Limited to P05 initial production blades; 373 engines
- Field plan in place for in-service inspection and replacement at shop visit
- Improved designs available
• Shank Cracking
- One event in over 9 million hours in CFM56 3D aero HPT blade fleet
- Root cause understood; cracking due to material property degradation from coating
- Factory engine testing, field blade retrieval on-going to characterize coating populations and life
capabilities
- No field action required at this time
• Airfoil Separations
- Four events in -5B/P and -7 fleets
- Telemetry testing has identified potential root cause; analysis underway - additional testing planned
- No field action required at this time
• Trailing Edge Separations
- Root cause identified, improved processes incorporated
- CFMI working to identify affected population
- CFMI will continue to update at WTT calls
Summary
HPT Blade

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CFM HPT Blade - Overview

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