By Dale Harper and Gary Tydings
Most metals can be melted and “atomized” by liquid (normally water) or gas to form etal powders. Atomization is the most
common method for producing metal and pre-alloyed powders, or powders consisting of two or
more elements alloyed in the powder manufacturing process. Powder materials include iron and
steel, stainless and nickel, tool steel, aluminum
and copper, and their many alloys. Iron and steel
account for 80 percent by weight of all metal powders produced annually.
Atomization accounts for nearly 70 percent by
weight of all metal powders produced in North
America. It is the main process for powder production because of its high production rates and economies of scale. Atomization also is the only way to
produce pre-alloyed powders.
Producing metal powders involves melting raw
materials in a crucible (induction melting furnace or
electric arc being most common) and then pouring
liquid metal into a vessel through one or several ori-
fices (see Figures 1 and 2). When the melt stream en-
ters the vessel, the liquid metal is atomized by either
water or gas, forming a spray of solid-state particles
that can be irregular, pear, or spherical in shape.
Atomizers are sized by the melt capacity of the
furnace, which may range from production batches
of 250 kilograms to 100 tons (see Figure 3). Powder
production generally is optimized for its intended
particle size distribution. Particle sizes range from
submicron to 600 microns, depending on the finished product specification. After the powders are
processed, they are classified, inspected, packaged,
Markets for Powdered Metal
Powdered metals are used in many areas of manufacturing, including business machines, the electronics sector, and telecommunications. Generally,
though, powdered metal technology falls into three
The first is powder metallurgy. To make P/M parts,
hot-forged and hot-isostatic-pressure (HIP) technologies press and sinter the powdered metal to net
or near-net shapes. This process mainly uses iron-based alloys.
The second is additive manufacturing. Working
from a 3-D model, electron beam and laser sintering technology build up A/M parts layer by layer. Additive manufacturing is used for small, complex, or
customized precision parts. Alloys include maraging steels, stainless steels, nickel-based materials,
cobalt-chrome, titanium, and aluminum.
The third technology area for powdered metals
involves thermal spray and weld overlay coatings,
surface treatment and enhancement methods processed through specialized equipment. The metal
powders used here mainly include nickel-, cobalt-,
and copper-based alloys.
P/M is by far the largest market for metal powders.
It represents about 80 percent of the total metal
powder tonnage consumed in North America. Conversely, the A/M market is a developing one.
For those in welding and metal fabrication,
though, the third area for metal powders—thermal
spray and weld overlay—is probably the most familiar. It’s a smaller market, but it’s also one of the
Thermal Spray Applications
Thermal spray is a surfacing technology in which
metal powder is used to add to or modify the surface of a component to enhance its design and application functionality. It is recognized by the American Welding Society (AWS) as a group of processes
in which finely divided metallic or nonmetallic powders are melted and accelerated onto the surface of
a part to form a coating. The molten (or semimol-ten) particles of sprayed material plastically deform
upon impact with the prepared and roughened surface, forming a mechanical bond.
According to a 2014 report from TechNavio Insights, the thermal spray market is shared by North
America ( 33. 2 percent), followed by Europe and the
Middle East ( 31 percent), and the rest of the world
( 35. 8 percent). The report breaks down the market
into coating service providers ( 75 percent), materi-
als ( 20 percent), and equipment-makers ( 5 percent).
Aerospace precision parts coating is the largest
application for thermal spray. Coatings protect the
aircraft engine turbine blades and combustion lin-
ers from extreme temperatures and pressures.
Meanwhile, coating demand for biomedical and
medical instruments is expected to grow significantly
over the next seven years. Thermal spray coatings
improve wear resistance and boost biocompatibility
of medical implant prosthetics and dental implants.
In the industrial markets, significant growth has
come from companies using thermal spray coatings as an alternative to hard-chrome plating,
which has regulatory restrictions and environmental implications.
A gas atomizer produces metal powders used in thermal
spray and weld overlay applications.
The solid state of metal
powders in metal fabrication
Thermal spray and weld overlay applications
are poised for growth