As part of a long-term collaboration with the Original Equipment
Manufacturer (OEM) Rolls-Royce Deutschland (RRD) in Oberursel, the
Fraunhofer Institute for Laser Technology ILT, working together with
the Chair for Laser Technology LLT at the RWTH Aachen, has developed an
innovative and cost-efficient repair technique for engine components.
|
TRUMPF laser cladding machine, equipped with a flash-lamp excited Nd:YAG-laser.
Picture source: Rolls-Royce Deutschland, Oberursel. |
 |
Repair process of an engine component.
Picture source: Fraunhofer Institute for Laser Technology ILT, Aachen. |
Ensuring flight safety is regarded as the number one priority in civil
aviation. One of the key strategies to achieve this is by maintaining
reliable engine performance, which is why engines undergo regular,
thorough inspections in which they are completely disassembled and
comprehensively serviced. The components of the engine that are made
from titanium and nickel-based alloys (superalloys) are subject to
heavy wear due to extreme fluctuations in pressure and temperature. In
addition, they are frequently damaged by foreign bodies that are sucked
into the engine during take-off and landing. Until recently, it was not
a feasible option to carry out the kind of special repairs that
involved having to replace sections of worn materials. Components that
could not be repaired therefore had to be replaced in their entirety.
As well as being extremely expensive, these replacement components were
often difficult to get hold of due to material availability problems in
the global market.
Researchers from the Fraunhofer ILT and the LLT have now succeeded in
surmounting these difficulties by using a laser cladding technique that
enables these defective engine components to be repaired. "What is so
innovative is the fact that we can take oxidation-sensitive titanium
materials and components that have a tendency to distort and weld them
in a precise and reproducible manner without any distortion," explains
Dr. Andres Gasser, project manager at the Fraunhofer ILT. "A local gas
atmosphere is used to prevent the molten weld pool generated in the
cladding process from reacting with the surrounding atmosphere. With
this method we can avoid the need to use a costly processing gas
chamber."
The Aachen-based research institute is able to take on
responsibility for handling the entire project, ranging from process
development and certification to installation of a system for laser
cladding at the site of the industrial project partner.
Using this new technique, a local weld pool is generated by the laser
beam on the surface of the component. A specially designed powder feed
nozzle then introduces a metal powder composed of a similar material.
The resulting layer possesses similar mechanical properties to those of
the component. "One of the keys to this technique is a newly developed
system of powder feed nozzles, which increases the efficiency of powder
use while preventing oxidation of the layers," explains Gerhard Backes,
project manager for nozzle development at the LLT. Thanks to the
special nozzles' modular configuration and compact design, the range of
possible applications is virtually unlimited. A further advantage of
laser cladding in comparison to conventional welding is the fact that
the low thermal load helps to minimize component distortion while
ensuring that the weld is free from defects and smoothly contoured to
the shape of the component.
In parallel to developing the process, the Fraunhofer ILT supplied a
modified laser cladding machine produced by the company TRUMPF, which
has now been up and running at Rolls-Royce Deutschland for around one
year, where it has been producing superb results. Martin Spallek,
responsible for component repair at RRD, sums up the developments so
far: "By deploying this repair technique we have managed to reduce the
time required for general overhauls of the engines by approximately one
third while simultaneously cutting costs. That has made a huge
contribution towards boosting our competitive advantage."
The innovation cluster "Integrative production technology for
energy-efficient turbomachinery - TurPro" set up by the
Fraunhofer-Gesellschaft is further enhancing this repair technique for
turbomachinery components. This will mean that the technology can also
be applied to land-based turbines, opening up new potential for general
types of engine technologies and - over the long term - for the entire
field of mechanical engineering. An impressive way of making a lasting
contribution towards securing Germany's status as a high-wage location.
back
top
