Exploring a novel approach for improving turbine wheel quality using eddy current inspection.

1. Defect Detection & Prevention
In Cast Turbine Wheels
Jack Rose
September 2015
Public Classification
A novel approach for improving
turbine wheel quality using eddy current
inspection

2. Public Classification

3. Turbocharging
Increased
POWER and
EFFICIENCY
Speeds exceed
200 000 rpm
Greater than
700ºC
Public Classification

4. Public Classification

5. Public Classification
Turbine wheel basics

6. Public Classification
Turbine wheel basics

7. New Cast Turbine Wheel Failed Turbine Wheel
Public Classification

8. Casting defect 1mm
2mm
0.25mm
Public Classification
Blade root
Turbine blade
fracture surface

9. Area of
Interest
Public Classification 86mm

10. How can we
detect these
defects?
Public Classification

11. Solution?
Manufacture of bespoke flexible
array eddy current probe by Eddyfi
Public Classification

12. Public Classification
Probe setup
Scan Parameters
Y –Axis scan speed 10mm/s
Frequency 1 500kHz
Frequency 2 300kHz
 The probe contains 15 x 2.2mm
diameter coils
 The coils are mounted onto a flexible
wear resistant plastic
 The coils are organised in transmit
and receive configuration with 8 coils
on row 1 and 7 coils set behind in row
2.
 An additively manufactured plastic
probe guide fit between the wheel
blades to guide the probe along its
scanning path.
 The coils are in a pancake form each
with ferrite cores.

13. Public Classification

14. Probe capability
Public Classification
All dimensions in mm

15. Artificial slot on machined
surface
Public Classification

16. Sub-surface artificial
holes
Public Classification
50mm
Scanning surface
and direction

17. 0.1mm
0.25mm
0.5mm
0.75mm
Distance
Sub-
surface
500 kHz 300 kHz
Public Classification
0.75mm
0.5mm
0.25mm
0.1mm
0.75mm
0.5mm
0.25mm
0.1mm

18. Real defect on
real component
Public Classification
The animation
is just a
representation
Turbine blade

19. Real defect on real component
300kHzscan500kHzscan
Public Classification
Vpp = 0.56V
Vpp = 0.31V
35mm

20. Public Classification
Defect detected by 3DXRCT and analysed at the University of
Manchester (MXIF) highlighted artificially in blue
Pressure surface

21. PREVENTION
Supplier Collaboration
1. Identify process that
introduces defects into
casting
2. Consider methods for
reducing effect of this
process
3. Monitor defect count on
casting optimisation trials
4. Perform durability tests to
validate improvements by
eddy current inspection
Public Classification

22. Baseline Results
Public Classification
Blades scanned = 576
1 2 3 4 5 6 7 8 9 10 11 12
Blade Number
Defect Blade Distribution
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3
Voltage
Voltage Distribution
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360
Phase Angle
Phase Angle Distribution

23. Further work
Public Classification
Currently testing 9 options for quality improvements that examine:
 Third tier supplier quality (alloy bar quality)
 Casting parameters modifications
 Additional steps to manufacturing that could improve quality