Aerospace gas turbines require a large number of small diameter holes (<1mm) to provide cooling in the turbine blades, nozzle guide vanes, combustion chambers and afterburner. Many thousands of holes are introduced in the surface of these components to allow a film of cooling air to flow over the component. Laser percussion drilling with pulsed Nd: YAG laser is now a well-established material processing technique in the aerospace industry. The advantages of using pulsed Nd: YAG laser of being able to drill difficult materials, especially superalloys and thermal barrier coated superalloys (TBC).

One of the major aspects that concern the aerospace industry is the quality of the drilled holes. Hole geometry such as taper, roundness and variation between holes must be within certain tolerances if the component is going to be used in an aero engine. Other important factors with respect to hole quality are metallurgical issues concerning recast layer and micro-cracking with in the hole.

This paper investigates laser percussion drilling of high quality holes for the aerospace market with a new low cost high peak power up to 20kW and high beam quality (<4mm.mrad) pulsed Nd: YAG laser especially developed for aerospace market. Holes were drilled with various laser and processing parameters on coated and uncoated nickel based superalloy material to examine the hole quality in terms of recast layer, taper, oxidised layer and cracking etc.

1.
Van Dijk
,
M.H.H
,
de Vilrger
,
D
and
Brouwer
,
J.E
,
Laser Precision Hole Drilling in Aero-engine Components
,
Proc 6th Conf lasers in Manufacturing
,
May
1989
ISBN 1-85423-047-6, Page No
237
247
2.
Disimile
,
P.J
, and
Fox
,
C.W
, “
An experimental investigation of the airflow characteristics of laser drilled holes
,”
Journal of Laser Applications
, Vol
10
No
2
,
April
1998
, Page
78
84
3.
Sivakumar
,
R
and
Mordike
,
B.L
, “
High temperature coatings for gas turbine blades
”, a review,
Surf. Coat Technol
.
37
(
1989
), page
139
160
4.
Miller
,
R.A.
and
Lowell
,
C.E
, “
Failure mechanisms of thermal barrier coatings exposed to elevated temperatures
”,
Thin Solid Films
95
(
1982
), page
265
273
5.
Tsui
,
Y.C.
and
Clyne
,
T.W.
Adhesion of Thermal Barrier Coating Systems and Incorporation of an Oxidation Barrier Layer
”,
Proceedings of Thermal Spray: Practical Solutions for Engineering Problems, Proceedings of the 9th Natural Thermal Spray Conference
,
ASM, Cincinatti
,
1996
, page.
275
284
6.
Corcoran
,
L.
Sexton
,
B.
Seaman
,
P.
Ryan
,
G.
Byrne
, “
The laser drilling of multi-layer aerospace material systems
”,
J. Mater. Proc. Tech
.
123
(
1
) (
2002
), page
100
106
.
7.
J.
Kamalu
,
P.
Byrd
,
A.
Pitman
, “
Variable angle laser drilling of thermal barrier coated nimonic
”,
J. Mater. Proc. Tech
.
122
(
2002
) page
355
362
.
8.
Itoh
,
T.W. Clyne
, “
Initiation and Propagation of Interfacial Cracks during Spontaneous Debonding of Thermally Sprayed Coatings
”, in:
Proceedings of Advances in Thermal Spray Science and Technology
.
Proceedings of the 8th Natural Thermal Spray Conference
, ASM,
Houston, Texas
,
1995
, page
425
431
.
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