AMMJ - Library

AMMJ Laser Cladding 10
REPAIR OF COMPRESSOR SHAFT
The compressor shaft is made of martensitic stainless
steel AISI 410 (DIN 1.4006 / X12Cr13). Near the end of
the shaft an area with an axial length of 70 mm was worn
off. The total length of the shaft was about 3,7 m and
the weight was about 1 ton. For laser cladding, stainless
steel powder AISI 316L is used as feedstock. A coating
with a total thickness of 2 mm is required. Since it is not
possible to obtain a coating with a thickness of 2 mm
after a single pass, multiple layers are applied on top
of each other. The typical maximal layer thickness for a
single pass is 1-1,2 mm. After laser cladding about 0,2
mm of the thickness needs to be removed to obtain a
smooth surface.
PRELIMINARY TESTS
Before treating the shaft, experiments are performed on a small bar to
evaluate the quality of the coating in terms of absence of cracking, the
degree of deformation of and the bonding to the substrate. To evaluate the
deformation behaviour, a bar with a diameter of 30 mm and length of 700
mm was cladded at both ends over a length of 20 mm. The results of a
run-out were satisfactory and showed a deformation of only 0,02-0,04 mm.
The cross section of the coating near the beginning is shown in Figure 3.
No cracks in the coating or in the martensitic stainless steel substrate are
present.
Due to the presence of key-seatings, which did not need to be treated,
copper inserts were placed at these positions to prevent these areas being
damaged by the laser beam. The stainless steel 316L material does not
adhere to the copper and the copper insert can be easily removed after
laser cladding.
LASER CLADDING OF SHAFT
The same laser cladding parameters as used in the preliminary tests were applied during laser cladding of the
shafts. The experimental setup is shown in Figure 4. The presence of the copper insert at the key-seatings is
visible at the left image of Figure 4. Two layers of stainless steel are applied on top of each other. The shafts
are machined afterwards and the repair was positively evaluated: adequate thickness and good bonding of
coating to substrate, minimal deformation induced by laser cladding, and no porosity in coating.
Figure 4 Setup used for laser cladding of compressor shafts
Figure 2 Laser cladding setup used in the study.
Figure 3 Cross section of AISI 316L
on a AISI 410 stainless steel substrate
Vol 24 No 1