WELDING
High-speed
WELDING
An extreme high-speed laser deposition welding (EHLA) method
is capable of coating large-area components at a rate of over
250cm2 per minute.
The EHLA method, which is signi cantly
faster than conventional laser
deposition welding, was developed
and patented by the Fraunhofer Institute for
Laser Technology (ILT) with the primary aim of
executing coating processes very quickly with
low layer thicknesses for rotationally symmetric
components. Now, laser system manufacturer,
TRUMPF is putting it into series production.
Antonio Candel-Ruiz, an expert for laser
surface methods at Trumpf, explains: “For
EHLA, we can draw on similar techniques that
we’ve been using for laser deposition welding.”
A tried-and-true method in metal coating for
many years, laser deposition welding delivers
high-quality results. This method makes it
possible to manufacture crack-free and virtually
pore-free coatings with metallurgical bonding to
the substrate out of a variety of materials.
“For large-area coating tasks, however,
lasers have lacked the necessary speed,” says
Candel-Ruiz. In addition, the minimum layer
thickness was around 500 micrometres (m);
thinner layers simply were not possible.
How EHLA works
Marco Goebel, Trumpf’s industry manager
for surface technologies, LMD, explains how
laser deposition welding normally works:
“We use a laser as a heat source to generate
a melt pool, and we inject powder particles
which are molten before the powder
particles touch the melt pool on
the substrate. By spinning out
parts which are predominantly
potentially asymmetric very
rapidly we are able to deposit
very thin, metrologically
bonded coatings on the
substrate with various kinds of
di erent metals.”
Whereas normal laser
deposition welding can coat 10
to 40cm2 per minute, the EHLA
titanium will not go
together. But we can
use nearly every metal
which is available as
method can achieve rates of over 250cm2
a powder for that
per minute. In addition, thinner coatings with
layer thicknesses of 10 to 300m are possible.
What’s more, EHLA permits a much ner laser
focus as well as using higher heat to melt the
powder, rendering the process considerably
more energy e cient.
One application where TRUMPF is using
the EHLA process is on brake discs to make
them more durable and stop them shedding
ne particles of brake dust that contributes to
air pollution. If a hard, corrosion resistant layer
is added there is less abrasion and therefore
less ne dust. It also means that braking
performance may last longer.
“The ne dust produced in our cities is 30%
brake dust,” says Goebel. “It might come up
in the future, and for sure it will come up in
the European Union as
a topic, that we have to
reduce the ne dust. As always
Steel and
process
in politics you cannot really foresee when it will
happen, but it will de nitely happen.
“We strongly believe, and we have
indication, that there might be a change in the
next couple of years and that will mean that we
are quite prepared. The European Union always
takes a while, but when the law comes through
usually you have to ful l it immediately and that’s
why we are preparing.”
Goebel goes on to say that there are
many other applications in which EHLA can
be used. For example, in the mining industry
where hydraulic components are under high
loads when making and supporting tunnels.
Alternatively, in the oil and gas industry where
hydraulics are used to keep drilling platforms
level under extreme pressures.
30 www.materialsforengineering.co.uk Winter 2019
/www.materialsforengineering.co.uk