Page 7 - Thermal Spray - Hi-Tech Compressor

The HVOF coatings
GOULD PUMP BEARING HOUSING
PLASMA: HVOF: (HIGH VELOCITY OXYGEN FUEL) produced by using
Sulzer Metco’s Hybrid
The plasma spray process (non-transferred arc) The HVOF process combusts oxygen and one of a select Diamond Jet System
uses inert gases fed past an electrode inducing group of ignitable gases (propylene). Although the HVOF and HVOF powders
the “plasma” state of the gases. When the gases system uses the basic principles of combustion, the spray exhibit the following
exit the nozzle of the gun apparatus and return to gun is designed di erently than the standard oxy-fuel attributes:
their normal state, a tremendous amount of heat is spray. The HVOF gun di erences produce higher ame
released. A powdered coating material is injected PUMP HOUSING temperatures and higher velocities. The result is more ► Excellent wear resistance
into the plasma “ ame” and propelled onto the thoroughly melted powder and more kinetic energy avail- for extended longevity
substrate. Typical coating materials include ceram- able to “ atten” the molten particles of coating material. of many costly parts and
ics (chrome oxide, aluminum oxide, zirconia and The HVOF process produces superior bond strength (cur- components that are
titania). The gas temperature range is typically 30,000 rently tested at 13,765 psi average) and coating density. exposed to harsh service
environments
– 60,000°F with our 1,000 amp recti er and a particle Typical coating materials include tungsten carbides. The
velocity range of 800 – 1,800 fps. gas temperature range is typically 6,000°F with a particle ► Superior micro hard-
ness compared to other
velocity range of 2,400 – 3,200 fps. thermal spray technolo-

STEAM TURBINE SEAL JOURNAL gies
► High adhesion to
the substrate - bond
The principle of plasma spray- strength of some coat-
Plasma gas + current ing is shown schematically to ings exceeds 83 MPa
Water-cooler anode the left. A high frequency arc (12,000 PSI)
Cathode is ignited between an anode
Coating and a tungsten cathode. The ► High density with low
gas owing through between porosity
the electrodes (i.e., He, H2, N2 ► Low residual stress and
or mixtures) is ionized such fewer impurities than
that a plasma plume several low velocity combustion
centimeters in length devel- thermal spray
ops. The temperature within
the plume can reach as high ► High thickness limits
as 16,000° K. The spray mate- - greater than 6.3 mm
rial is injected as a powder (0.250”)
outside of the gun nozzle into ► Excellent machinability/
Powder port Workpiece the plasma plume, where it is surface nishing.
Insulator melted, and hurled by the gas
onto the substrate surface.

RIVER WATER
PUMP SHAFT STRAINER W/ SHAFT CONVEYOR ROLLERS PISTON ROD OD GRINDING B E F O R E A F T E R
POWER CYLINDER HEAD – GASKET SURFACE