Until now, laser drilling has been achieved by pulsed beams through percussion, trepanning, and the combination of both. Problems often encountered for the production of cooling holes in aerospace nickel alloys include recast layer formation, tapering, hole repeatability (particularly when percussion drilling is used) and back wall strike for hollow components. This paper reports for the first time, a new laser drilling technique based on a continuous wave 1 kW single mode fibre laser. Vertical holes are drilled in nickel based super-alloy plates using a continuous wave (CW) and pulsed mode drilling methods. Zero tapered holes with negligible recast layer formation and free from micro-cracks are demonstrated when drilling in both single crystal CMSX-4 and Hayness 230 materials under the CW mode. The hole diameter has been reduced to less than 0.2 mm for a material thickness of 2 mm. The drilling and breakthrough time are measured using photodiode and high speed imaging techniques as 2.2 and 0.8 ms (100-200 times faster than standard Nd:YAG laser drilling). Process monitoring by a high speed camera images and the photodiode also revealed that material removal is characterized by a bulky downward ejection after the hole breakthrough. Elimination of the upward material ejection with a CW pulse provides less erosive flow on the walls. Unique process mechanisms leading to high speed production of recast free parallel holes with the high brightness fibre laser are presented.

1.
Corcoran
A S L
, and
Seaman
B
(
2002
)
The laser drilling of multi-layer aerospace material systems
Journal of Materials Processing Technology
123
100
6
2.
Van Dijk
M H H
,
Vilrger
,
D.
,
Brouwer
,
J.E.
(
1989
)
Laser Precision Hole Drilling in Aero-Engine Components Proceedings of Sixth International Conference on Lasers in Manufacturing
237
47
3.
Vander Wert
T L
,
Prairie
,
E.
(
1994
)
Lasers Take On Hole-Making Challanges Modern Machine Shop
67
62
7
4.
Bandyopadhyay
S
,
Sarin Sundar
J K
,
Sundararajan
G
and
Joshi
S V
(
2002
)
Geometrical features and metallurgical characteristics of Nd:YAG laser drilled holes in thick IN718 and Ti-6Al-4V sheets
Journal of Materials Processing Technology
127
83
95
5.
Low
D K Y
(
2001
)
Spatter and Taper Control in Laser Percussion Drilling
, PhD Thesis. (
Manchester
:
UMIST
)
6.
Low
D K Y
,
Li
L
and
Byrd
P J
(
2000
)
The effects of process parameters on spatter deposition in laser percussion drilling
Optics & Laser Technology
32
347
54
7.
Sezer
H K L
,
L.
Schmidt
,
M.
Pinkerton
,
A.J.
Anderson
,
B.
Williams
, P. (
2006
)
Effect of beam angle on HAZ, recast and oxide layer characteristics in laser drilling of TBC nickel superalloys
International Journal of Machine Tools and Manufacture
46
1972
82
8.
Tiffany
W B
(
1985
)
Drilling, Marking and Other Applications for Industrial Nd:YAG Laser Proceedings of the SPIE 527
28
37
9.
Voisey
K T
,
Clyne
,
T.W.
(
2004
)
Laser Drilling of Cooling Holes Through Plasma Sprayed TBCs Surface & Coatings Technology
176
296
306
10.
Yilbas
B S
,
Aleem
,
A.
(
2003
)
Laser hole drilling quality and efficiency assessment
Proceedings of the Institution of Mechanical Engineers Part B-Journal of Engineering Manufacture
218
225
9
11.
Chichkov
B N
,
Momma
,
C.
,
Nolte
,
S.
,
von Alvensleben
,
F.
,
Tunnermann
,
A.
(
1996
)
Femtosecond, picosecond and nanosecond laser ablation of solids
Applied Physics A Materials Science & Processing
63
109
15
12.
Feng
Q
,
Picard
,
Y.N.
,
Liu
,
H.
,
Yalisove
,
S.M.
,
Mourou
,
G.
,
Pollock
,
T.M.
(
2005
)
Femtosecond laser machining of a single-crystal superalloy
Scripta Materiala
53
511
16
13.
Weck
A
,
Crawford
,
T.H.R.
,
Wilkinson
,
D.S.
,
Haugen
,
H.K.
,
Preston
,
J.S.
(
2008
)
Laser drilling of high aspect ratio holes in copper with femtosecond, picosecond and nanosecond pulses
Applied Physics A Materials Science & Processing
90
537
43
14.
Ancona
A
,
Roser
,
F.
,
Rademaker
,
K.
,
Limpert
,
J.
,
Nolte
,
S.
,
Tunnermann
,
A.
(
2008
)
High speed laser drilling of metals using a high repetition rate, high average power ultrafast fiber CPA system
Optics Express
16
8958
68
15.
Brajdic
M
,
Walther
,
K.
,
Eppelt
,
U.
(
2008
)
Analysis of laser drilled deep holes in stainless steel by superposed pulsed Nd:YAG laser radiation
Optics and Lasers in Engineering
46
648
55
16.
Dietrich
J
,
Brajdic
,
M.
,
Walther
,
K.
,
Horn
,
A.
,
Kelbassa
,
I.
,
Poprawe
,
R.
(
2008
)
Investigation of increased drilling speed by online high speed photography
Optics and Lasers in Engineering
46
705
10
17.
Sobih
M
,
Crouse
,
P.
,
Li
,
L.
(
2008
)
Striation-free fiber laser cutting of mild steel sheets
Journal of applied physics A
90
171
18.
Li
L
,
Sobih
,
M.
,
Crouse
,
P.L.
(
2007
)
Striation free laser cutting of mild steel sheets Annals of the CIRP
56
19.
Naeem
M
,
Keen
,
S.
(
2009
)
Dual Mode High Brightness Fiber Laser for Ablation and Drilling of Aerospace Superalloys
. In:
ICALEO
, (
Orlando, FL
20.
Harp
W R
,
Dilwith
,
J.R.
,
Tu
,
J.F.
(
2008
)
Laser ablation using a long-pulsed, high-fluence
,
CW single-mode fiber laser Journal of materials processing technology
198
22
30
21.
Sezer
H K
(
2007
)
Laser drilling of Thermal Barrier Coated jet engine components
, PhD Thesis.
Manchester University
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