How a new Nano-Manufacturing process is making steel 10x stronger
By Frank Rovella
Seattle-based Modumetal is in the early phases of testing a
new type of nanolamination coating process that has the potential to reshape
the metal manufacturing industry. By creating multiple discrete layers only
nanometers thick they are able to impart characteristics such as high strength
and corrosion resistance and do it very economically. Until now, the only way to get these qualities was through
the use of high-strength alloys or with methods such as heat treating, ion
implantation, or a number of plating and coating processes. All of these can be
very cost-effective in limited quantities but, for industries that consume
large amounts of steel such as petro-chem, oil & gas, and construction
there is no low-cost solution.
Seattle-based Modumetal is in the early phases of testing a
new type of nanolamination coating process that has the potential to reshape
the metal manufacturing industry. By creating multiple discrete layers only
nanometers thick they are able to impart characteristics such as high strength
and corrosion resistance and do it very economically. Until now, the only way to get these qualities was through
the use of high-strength alloys or with methods such as heat treating, ion
implantation, or a number of plating and coating processes. All of these can be
very cost-effective in limited quantities but, for industries that consume
large amounts of steel such as petro-chem, oil & gas, and construction
there is no low-cost solution.
The concept of creating laminations using nanolayers is not
new; however, Modumetal’s application method is. Previously, nanolaminates
could only be created via a vapor deposition process the problem is that it’s
expensive and not easily scalable. Modumetal’s process takes a markedly
different approach; though simple in nature, its success hinges on precise
chemistry and process parameters. It’s
based on hydrolysis, similar to the electroplating process, and utilizes a
submersion bath. But, unlike electroplating, it relies on hyper exact amounts
of electrical current applied at specific intervals. The bath contains
predetermined types of metal ions that allow for the creation of distinct
alloys; this means that each layer can be composed of a different
material. Multiple layers may be applied to total up to one centimeter thick. This flexibility in layer composition
allows for the engineering of custom nanolaminations that can provide whatever
characteristics the application requires.
To understand how high strength and corrosion resistance can
be applied to a metal with what is essentially a coating, we need to consider
scale. For example, electroplated layer thicknesses typically run between 5 to
100 microns, 1 micron (µ) = 0.00003937 inches, while 1 nanometer (nm) =
0.000000039 inches. This is on the atomic scale; to put that into perspective,
0.1 nm is the diameter of a helium atom. As the image below highlights, at the nanoscale, our understanding
of surface profile changes. There is far more surface area to work with, which
means greater adhesion can be achieved. At this scale, the metal ions become a
physical part of the substrate. The ability to dial in an alloy combination to address a
specific corrosion requirement outside of a steel mill is unprecedented, but
the main component that makes this technology so attractive is strength.
 |
| Carbon steel surface taken through an electron microscope, the actual size is 10 micrometers (µm) across that is equal to 10,000 nanometers. |
Tensile strength is a material’s ability to withstand
pressure before failing, and failing begins with cracking. To demonstrate how
nanolaminations can make steel 10 times stronger, think about a sheet of
plywood; this is the most common example of a lamination. Plywood contains multiple layers of materials
with different strength characteristics and varying grain structures—the more
layers added the greater the strength. The strength is further enhanced when
the lamination is nailed or glued into place. Now imagine a cross-section of
structural steel with all of its surfaces encapsulated in layers of nanometer-thick superalloys of varying compositions, bonded to the substrate at the
atomic level. The advantages are obvious.
 |
| Stress cracking in a cross-section of stainless steel pipe. |
The potential this has for large-scale applications such as
those found in oil & gas and the construction industries could be a game-changer. But to gain a foothold in manufacturing, a lot more data will be
needed, and many questions will need to be answered. Beginning with the
application process, will it be better suited for pre or post-treatment? Will
ductility be affected, how will it react to rolling or stamping, and what about
welding? The ability to weld treated
metals could be one of the key questions; this is essentially a coating—when
it’s welded what happens at the joints? Even coatings a centimeter thick will
be burned through, leaving a seam of bare substrate. However, these issues may
already be moot points, as Modumetal is currently ramping up its production
facility in Washington State. Of course, before this resembles anything close
to wide-scale adoption, all of the standard bodies including ASTM, API, ASTM,
and CEN will have to give it their blessing, and that certainly won’t happen
overnight.
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