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Since the beginning of metallurgy, the properties
of materials and composites have been constrained by solubility
limits, diffusion coefficients, and compatibility of physical and
chemical constituent properties. Alloys
average the mechanical properties of the constituent metals and
the property extremes are lost. To escape these limits of nature,
ingenious — now conventional — ways
of combining strength, toughness, and wear resistance have been devised using
various coatings and laminations. In about 80% of carbide tool applications,
tungsten carbide wear performance is improved via external coatings
that are only about 1/5 to 1/4 the thickness of a human hair. Such
tools are systematically discarded after only about 10% of their
wear tolerance has been used.
Tough-Coated Hard Powders (TCHP), or EternAloy®,
patented by Allomet-USA (U.S. Patent No. 6,372,346 et al.),
are extremely hard refractory particles CVD coated with nanolayers
of (1) WC or TaC and (2) Co or Ni binder (see Figure 1).
TCHP enables us to nanoengineer material properties. Encapsulating
fine particles having one set of desirable properties with grain
boundary modifiers having other properties allows us to blend heretofore-uncombinable
material-property combinations prior to sintering. This allows the
materials engineer to “alloy” materials previously “un-alloyable.”
With over 30 candidate core materials, thousands of EternAloy®;
combinations are practically possible. EternAloy®; allows us
to engineer almost any properties we can imagine (e.g., light
weight, low coefficient of friction, high or low thermal conductivity,
lubricity, …) in sintered materials, and the applications
seem limitless.
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This merging of multiple property extremes into
all-in-one “designer particles”
enables an unprecedented near-atomic scale integration of thermodynamically
incompatible materials and properties so that they operate simultaneously
and seamlessly at the finest possible scale at working surfaces
and cutting edges of tools. The same principle has been proven effective
in thermally-applied coatings. The TCHP nanoencapsulated “building
block” TCHP particle contains all the essential elements (of
hardness + wear resistance + toughness + binder metal + other designer
properties) and gives the materials engineer thousands of new material
grades with engineered properties simultaneously optimized at the
nano-, micro-, macro- and functional levels.
Consolidation of TCHP creates an engineered highly
homogeneous cellular structure whose contiguous tough WC-Co “shells”
each contain a wear-resistant core (e.g., TiN). In TCHP’s,
the tough coatings chemically bond throughout the tool, combining
the strength, heat resistance, and toughness of cemented carbides
with the chemical and abrasion wear resistance of harder core particle
materials. As wear progresses, new wear-resistant material continuously
replaces the working surfaces and edges of the tool until its geometry
reaches its maximum limits. TCHP tools are then reusable many times
by relapping or electro-discharge machining (EDM).
EternAloy®; also has major applications
in aerospace, automotive, industrial, mining, petroleum
and natural gas drilling, and components because of
its light weight and unique properties.
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