Canadian Finishing & Coatings Manufacturing Magazine March/April 2022 - 32

PLATING AND ANODIZING: EHLA
is much less than with laser cladding. When this is combined
with low substrate heat-input and dilution, EHLA starts to
offer some interesting capabilities with different material
pairings (e.g steels, Al-, Co-, Ni-, and Ti- alloys) and behavioural
differences with hard facing materials, which often appear to
be less sensitive to cracking during deposition (e.g. Stellite 6,
Tribaloy T800, WC-Cermets).
What is EHLA is capable of, and what it is not capable of?
EHLA is currently only established for applying coatings on
rotationally symmetric components, such as shafts, rollers,
and discs. During the EHLA process, components are rotated
at several hundred, to several thousand, RPM to create the
required surface speed relative to a slower travelling nozzle. So
far, it has been
challenging to replicate the EHLA process on
a freeform surface, which would require high speed movements
of the nozzle and/or of the substrate within threedimensional
space. This would require complex manipulation of several axis
using advanced kinematics to achieve the necessary high speed
and accelerations of the end effector.
Companies and research facilities such as Ponticon (GER),
Fraunhofer ILT (GER) and TWI Ltd (UK) are actively working
towards the goal of freeform or 3D EHLA.
From a material selection and utilization aspect, EHLA
is capable of applying precision metallic and metal matrix
composite coatings for the protection against corrosion, wear,
impact, temperature, or permeation, at ultra-high-speeds. Like
most powder feed processes, not all of the feedstock material
is captured and used in the coating. Nevertheless, EHLA is still
considered a highly material efficient coating process, and with
process optimisation, over 90 percent of the feedstock powder
can be captured into the melt pool. Compared to some thermal
spray processes, EHLA is twice as efficient in terms of material
utilization, but also creates a stronger metallic bonding between
the coating and the substrate.
One area driving significant interest in EHLA is the potential
to replace chrome plating for a range of different applications.
The challenge of EHLA and all chrome plating alternatives, is
to match the cost of conventional chrome plating. EHLA may
have the potential to achieve this owing to its high coverage
speed, but with the added advantage of being friendlier towards
the environment and population through a broader range of
materials.
How much does EHLA cost typically?
It is rather difficult to give an exact or specific answer to how
much EHLA costs, as this is highly dependent on the application,
its size and its coating specification. More broadly speaking,
the costs can be broken down into the following three key
considerations (1) the cost of the powder, (2) the time needed to
produce the coating, and (3) the cost of the hardware. The cost of
the hardware is arguably the easiest to define. Companies such
as Hornet Laser Cladding BV and Trumpf GmbH can provide
dedicated EHLA machines. A turn-key EHLA solution could cost
from US$500,000 to over US$2M, depending on capabilities,
component/machine size, and additional features of the system.
A further consideration which can have a significant impact
on cost, is material utilisation. For example, weld overlay
processes, such as arc (e.g. MIG and TIG) and laser cladding,
often require a minimum coating thickness of over 1mm to
ensure required chemistry and material properties are achieved
at the finished surface, i.e. becoming free from the effects of
substrate dilution. Hence, EHLA can deposit less material and
still achieve the same requirement of the coating. Furthermore,
additional layers to give a machining allowance are often
applied, which in the case of EHLA, can be only a few tens of
microns more.
Significant and continued efforts are also underway to reduce
the cost of the coatings through powder optimisation including
alloy design, capital equipment availability and standardisation,
process robustness and automation, and improved coating speed
and efficiency.
I see that EHLA is popular in Europe. Do you think EHLA
will become more popular in North America in the future?
Europe received a head-start vs. the rest of the world, aided by
a combination of being home to its invention (Fraunhofer ILT,
Germany) [2] and linked partnerships with EHLA specific
equipment developers (i.e. Hornet Laser Cladding BV). North
America has always been highly active in areas of laser cladding,
thermal spray and also in evaluating
new and alternative
coating technologies. Hence, it is just a matter of time before the
message about EHLA, and its benefits, will be recognised more
widely in North America, and I hope this article, and TWI [3],
can play a part in its dissemination and exploitation.
Significant and continued efforts
are also underway to reduce the
cost of the coatings through powder
optimisation including alloy design,
capital equipment availability and
standardisation, process robustness
and automation, and improved coating
speed and efficiency.
References:
Setting Sights on a 3D Process, Schopphoven Thomas, Schulte Olive, Photonics View, 2019.
https://www.ilt.fraunhofer.de/en/media-center/brochures/b-protection-against-wear-and-corrosion-with-ehla.html
https://www.twi-global.com/technical-knowledge/faqs/what-is-ehla#:~:text=Extreme%20High%20Speed%20Laser%20Application%20(EHLA)%20is%20a%20novel%20
technology,Beam%20(DED%2DLB)).
32
www.cfcm.ca

https://www.ilt.fraunhofer.de/en/media-center/brochures/b-protection-against-wear-and-corrosion-with-ehla.html https://www.twi-global.com/technical-knowledge/faqs/what-is-ehla#:~:text=Extreme%20High%20Speed%20Laser%20Application%20(EHLA)%20is%20a%20novel%20 http://www.cfcm.ca

Canadian Finishing & Coatings Manufacturing Magazine March/April 2022

Table of Contents for the Digital Edition of Canadian Finishing & Coatings Manufacturing Magazine March/April 2022