der grains fall into the pool as it cools and bond to it, giving the surface a sandpaper-type feel. Though heat parameters can be increased to melt these grains, this tends
to overdilute the clad with the base metal. Third, some
powder doesn’t make it into the pool at all. Most
processes use up to about 90 percent of the powder. This
is light years ahead of legacy technology such as thermal
spray, but still, powder material can be expensive.
Figure 4 In hot-wire laser cladding, a heated wire is fed at an
angle into the melt pool created by the laser beam.
The Road to Hot-Wire Laser Cladding
“The ideal scenario would be to feed a solid material in
and not have any material loss,” said Brian Smith, sales
and application engineer at Alabama Laser. “Also, by
feeding a solid material in, you can go out-of-position.”
Initially Alabama Laser experimented by feeding a
cold wire into the laser melt pool. Though the process
worked for some applications, it was tedious. The deposition rate is slow, and cold wire must align perfectly with
the laser spot to produce satisfactory results.
“All the heat is coming from the laser,” Penn explained,
“and you have a smaller pool, so you have a smaller target
to hit.”
This is the reason engineers pursued what’s turning
out to be one of the company’s most promising new
processes: hot-wire laser cladding. The process combines
preheated GMAW wire with a multikilowatt, solid-state,
fiber-delivered laser (see Figure 4). It’s a bit like hot-wire
GTAW with the GTAW setup replaced by a laser beam.
Like the powder process, this kind of laser cladding also
produces a microns-thick dilution between the base and
clad metal (making a nearly chemically pure clad) and of-
fers increased deposition rates (see Figure 5).
Figure 5 This thick clad over a pipe section was deposited by
the hot-wire laser cladding process. It has an almost imperceptible dilution layer, making the clad almost chemically pure.
Figure 6 Hot-wire laser cladding deposited a thick clad layer of
INCONEL 600 series onto a bar, which was subsequently bent
without cracking—and with no heat treatment.
termines what works and what doesn’t. When you put
together all the parameters of the welding power source
and the laser, the matrix is huge.”
To maintain the needed level of control, information
automatically passes among the power source, the con-
trol, and the cladding head itself. To ensure everything is
lined up, the operator can use a video unit integrated into
the setup.
Potential in Oil and Gas Country
Sitting at his desk, Penn pointed to a metal sample with
a thick clad of 600-series INCONEL® alloy (see Figure 6).
“That was hot-wire laser-cladded, then bent—with no
heat treatment.” The sample is crack-free. “We’re proud of
that one.” This is possible, he said, because of the precise
control of heat in every part of the process. Energy levels
in both the GMAW power source and the laser can be
tweaked ever so minutely to produce the desired results.
Some of the attributes from hot-wire laser cladding
likely will raise eyebrows. Many in the oil and gas industry clad pipe using hot-wire GTAW.
“I’m no expert on hot-wire TIG,” said Penn, “but I can
report on what I’ve witnessed. I’ve seen deposition rates
being used in production from 2 to 3 pounds per hour.”
He smiled. “We can run rings around that now.”
Senior Editor Tim Heston can be reached at timh@the
fabricator.com. Images are courtesy of Alabama Laser,
55 Laser Blvd., Munford, AL 36268, 256-358-9055,
www.alabamalaser.com.
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