Problem: Heavy Duty Wear Protection (Slurry
Pumps and Mixer Blades)
Pumping fluids containing large concentrations
solids is extensively practiced in industry. However, this practice
can severely erode components that are used to move these materials.
Hard materials attached to high wear surfaces, have been used
to resist such erosion damage. These hard materials have typically
been clad on to surfaces via co-forming, polymer cements, brazing
and or welding, depending on the service temperatures and environments.
The most widely used technique is welding, but many times welding
can crack or distort the underlying components and only yielding
Ľ 25 volume % hard particles.
Mixer parts are similar to slurry pump components
in that mixers are move slurries, agglomerate mixes, highly
loaded "plastic" compounds, and other particulate
media. The mixer blades are exposed to low angle erosive action
or abrasion as the mixers run against container walls and high
frequency impact from large, hard particles. Thus, other coating/cladding
processes are needed to assure improved wear resistance. These
new coating must be metallurgically bonded, able to cover contoured
flow surfaces, and have a high hard particle content, while
being able to coat sharply contoured and re-entered surfaces
-M or S
BrazeCoat‚ -M and BrazeCoat‚
-S. mats and suspension coatings are applied to a wide variety
of contoured surfaces. The different types of BrazeCoat‚
coatings enable its application in a wide range of environments
and on a range of compatible base materials. BrazeCoatģ M (mats)
are able to be cut, placed and fused to large and small surfaces.
BrazeCoat‚ -S (suspensions) can be
sprayed or applied by dipping to cover even the complex surface
contours of impellers. BrazeCoat‚
is proven in erosive and abrasion with WC grades being superior
to the best flame spray and fuse coatings and having at least
4 times more erosion resistance than white cast iron. BrazeCoat‚
offers tailored thicknesses, hardness and coating thicknesses,
dependent on the need. The coatings are easily applied and fused
during post application furnace, treatments. The resultant metallurgical
bonds assure excellent adherence, even in the most abrasive
and erosive environments.
Additional Protection for Drilling Tools
Rock drilling equipment is normally protected
against wear via the use of carbide (WC) and/diamond inserts
brazed into the cutting edges. During drilling, these cutting
edges remove and crush the rock and soils as they pass by the
drilling bits non-cutting surfaces. Away from the cutting
edges, the tool bit surfaces still wear quicker than the cutting
edges themselves. This reduces the tool life and limits the
useful life of the carbide or diamond inserts. Weld overlays
and thermal spray coatings have been applied, but their variable
quality and process control lower their reliability as a solution.
-M or S
BrazeCoat‚ -M and BrazeCoat‚
-S are very hard, coatings produced from mats and suspension,
respectively, consisting of a high volume percent tungsten carbide
(WC) and/or chromium carbides (Cr3C2).
Either product can be used to coat contoured surfaces. The BrazeCoat‚
process utilizes a mat or suspension of carbide particles that
are subsequently infiltrated with an adjacent cloth or suspension
of a braze filler powders. The mats, up to 0.120" thick
are applied directly onto the fitting surfaces to be protected.
While the suspensions, typically sprayed on to Ľ
0.012" thick, coat more difficult tool surface geometries.
Infiltration, fusion and metallurgical bonding of the BrazeCoat‚
layers is accomplished in one step by heating in vacuum or H2
atmospheres. Once the fusion treatment is completed, the BrazeCoat‚
coatings exhibit wear behavior near that of cemented carbides
and protects longer and more consistently than welded or thermal
Problem: Protecting Turbine Blades (Z-Forms)
Turbine and other turbo-machinery blades, have
the tendency to vibrate and therefore require stiffening and
support. Many times this is accomplished by providing an integral
ring located either at the blade tips and/or mid-span. These
rings must be split to reduce fatigue cracking. However, the
ring segments, typically machined or cast into each blade, must
run and vibrate against the other blades ring segment.
The segments interlock as "Z" forms where on adjacent
"Z" surfaces highly wear resistant coatings are required
to prevent premature failure through fretting fatigue or impact
These coatings require high hardness, toughness,
excellent bonds and good oxidation resistant since, for turbine
blades the temperature could exceed 1800įF. These
highly stressed coatings and blade areas require high performance
and reliable coatings.
Currently, thermal spray and weld claddings are
used. These methods perform with varying degrees of success
and many times are expensive.
BrazeCoat‚ -M using
Cr3C2 carbides is a good cladding candidate
to replace either thermal spray coatings or weld overlay done
by plasma transferred arc or laser. The turbine blade base materials
are typically highly alloyed nickel based materials which can
easily crack when welded. Hence, welding processes have to localize
and minimize the heat effects. Thermal spray, on the other hand
is not material efficient due to the narrow edges to be coated
and does not readily achieve metallurgical bonds. Thus, thermal
spray coatings exhibit high occurrences of coating debond. BrazeCoat‚
-M, eliminates many of these problems. Importantly, the mats
can be cut to the size and geometry of any edge, are processed
in a thermally and environmentally controlled atmosphere, and
metallurgically bond to the blade materials. Compared to either
weld overlays or thermal spray claddings, BrazeCoat‚
s NiCrBSi matrix Cr3C2 filled claddings
exhibit improved wear resistance based on its improved bonds
and higher, more uniform carbide distributions.
For additional case histories of how MRis
BrazeCoat‚ has solved cladding or
wear prevention problems: e-mail: firstname.lastname@example.org