Laser application of metallic overlays to metallic substrates
offers properties similar to overlays applied by traditional
welding methods but with substrate metallurgy effects more akin to
sprayed and fused coatings. The result is a true metallurgical bond
of overlay and substrate with minimal dilution and low
heat-affected zone (HAZ). Laser-applied overlays do not require
masking for precise deposit geometry, and they can be tailored for
nearly any substrate/overlay pairing.
- Hard valves and seats
- Down-hole tools for oil and gas drilling
- Agricultural size-reduction tooling
- Extremely high-wear applications
Laser-applied overlays are produced by locally heating the
substrate metal to a molten state using a tightly controlled beam
of laser energy, and then introducing a feedstock of the overlay
material in powder or wire form. The melt pool produced by the
defocused laser beam absorbs the melted feedstock, and, as the beam
and powder injection are moved away, the material rapidly
solidifies, producing a fully dense weld bead. The welding
apparatus is attached to a motion control system—either a five-axis
CNC device or a six-axis robotic arm—which can be programmed to
precisely guide the tool over complex surfaces, yielding a uniform
overlay thickness over nearly any outer surface geometry.
Monitoring of the tool speed over the surface allows the system to
accurately throttle laser power and powder parameters to ensure
uniform coating properties despite acceleration and deceleration of
the tool by the motion control system.
All operations are fully automated, ensuring accurate and
repeatable application of the weld overlay. A single computer
system coordinates several subsystems managing motion, powder
feeding, laser operation, and other integrated processes such that
a single program can be used to define all operations for a given
part or overlay. Once the program is written and stored, the
overlay can be duplicated on any number of identical components.
Due to the precise control of the laser energy at the weld pool,
overlays can be tailored to provide optimal deposition efficiency,
thickness, and/or HAZ. Typical single-pass thicknesses can be in
the range of .015” to .060”, though other dimensions are possible.
Geometric accuracy of the overlay’s dimensions can be within a few
thousandths of an inch, depending on the shape of the weld border.
Other methods can be used to control the surface finish of the
overlay after application.
Laser Cladding Facts
Laser cladding offers an array of unique advantages over other
conventional welding and hardfacing methods...
- High purity, low dilution welded overlay
Overlay chemistry and hardness are undiluted at the surface of the
first pass; there is no need for multiple passes or heavy overlay
thicknesses that add expense and induce unwanted tensile stress.
- Very low heat input, low distortion
Fully machined parts with close tolerances can be welded with
little risk of distortion or dimensional deviation. Overlays have
been applied to substrates as thin as 0.060” (1.5mm) without
warping or distortion.
- Welded, fully alloyed bond
Unlike thermal spray, the bonding mechanism is molecular and not
mechanical. External physical stresses are unlikely to cause the
overlay to disbond, fracture, or spall. Overlays can withstand
significant abrasion and direct impact.
- Rugged, high toughness protection
Tungsten and titanium carbide composite overlays are regularly used
to protect drilling and mining components. Cobalt-based alloy
overlays defend against particulate erosion and cavitation in
high-pressure pumps, valves, and turbines.
- Impermeable corrosion barrier
Uniform, crack- and pore-free overlays prevent permeation and
attack of substrate materials by even highly reactive liquids and
gases. Overlays can be machined, ground, and lapped to form
tight-fitting seals for valves and couplings.
- Virtually unlimited metallic overlay-substrate combinations
Most overlay materials can be welded onto nearly any machinable
metallic substrate, allowing high-performance alloys or special
property materials to be added strategically to less-expensive free
machining steels or exotic aerospace alloys.
Laser cladding equipment system SM-111
Capabilities Overview of laser cladding
Our laser work centers are built for flexibility...
- Large 10’ x 5’ x 5’ work envelope
- Five-axis Cartesian and eight-axis robotic manipulators
- Multiple simultaneous powder injection
- Selection of lasers, wavelengths to suit application
- Highly variable focus and bead shape
- Advanced “flying optics” allow steep application angles
- Bead width and power adjustable while in motion
- Fully automated application, highly accurate and repeatable
- Sophisticated offline programming suite allows