Laser cladding is an additive manufacturing process. It utilizes a laser to metallurgically bond hard coatings to a product’s base material. Laser cladding enhances the component’s performance or longevity.
By using laser cladding in wearing parts, we can reduce process down times. Laser cladding is used for both new and old parts. The base material and coating material adhesion is metallurgic. Adhesion is similar to welding.
Laser cladding benefits
- Strong metallurgical bond, welded joint - in effect, a single part
- Low heat input => small deformation
- Impermeable => good corrosion resistance (one layer is sufficient)
- Low alloy => good corrosion and wear duration in one layer
- Minor changes in the structure and properties of the base material, small HAZ (Heat-Affected Zone)
- The coating features are "customizable"
Laser cladding, target properties
- Wear resistance
- Corrosion resistance
- Liquid corrosion resistance (chlorides, acids, bases, etc.)
- Heat Corrosion Resistance (Melt Resin, Oxidation)
- Improved sliding friction
- Repair / filling
- Environmentally friendly
- Increased product lifecycle
- Short turnaround (renewal, refurbishment)
Improve product properties and save costs by coating structural steel with acid-resistant coating.
Case Outotec, Turula engineering
Refurbishment of shaft with S355 + 316 acid resistant laser surface coating
In laser cladding a meltable additive is metallurgically attached to the molten surface of the base material by means of a laser beam applied to the surface.
Therefore, it is often relatively easy to choose the corrosion-resistant material that is to be applied with laser cladding, because often the material suppliers' manuals and different material selection guides can be used directly.
When the coating cools rapidly, it has a very fine microstructure and the corrosion resistance of laser cladding is even better than with rolled solid material.
Laser cladding process
- The coating additive is fed from a separate feeder to the laser beam
- The additive absorbs energy from the laser beam
- The additive is heated and melts
- The molten material is also metallurgically bonded with a laser beam from the surface to the molten parent material
- Coating layer is created
AISI431,316, tooling steel
Inconel®, Hastelloy®, Monell®, NiCr, NiCoBSi
- Coatings containing coarse particles, the softer additive acts as 'glue' for carbides
Co / Ni-based+ WC, Ni-based + CrC
Corrosion protection coating
Laser cladding is the ideal method for corrosion protection as it provides an impermeable, non-porous coating. As the coating cools rapidly, its microstructure is very fine and the corrosion resistance of laser coatings is even better than the rolled solid material.
The material selected for laser coating used for corrosion protection is often relatively easy to choose because often material guides for material suppliers and manuals can be used directly.
The most common types of wear are:
- Abrasive wear, i.e. wear caused by particle friction along a surface
- Erosion, when there is friction between a surface and a jet of particles
- Adhesive, wear caused by friction between moving parts in contact with each other
- Corrosion wear, fretting, cavitation, wear and tear, etc.
Corrosion and elevated temperatures are often associated with the above wear patterns. Different forms of wear also require different properties of the coating material. Against adhesive wear, most commonly used are stellites and Ni-Cr-B-Si alloys, whereas abrasive wear uses carbide-containing metal matrix composites in which tungsten, chromium, titanium, vanadium and similar are mixed with the metal matrix.
QUALITY CRITERIA OF LASER CLADDING MATERIALS
Laser surface treatment is a high quality surface treatment method, which is its most important characteristic. In most cases this means a dense and low alloy coating.
Impermeability refers to a coating with no cracks or pores. Especially under corrosive conditions this is an important criterion for laser coatings. Mostly, pores are found in highly carbon-containing mixtures. Such mixtures are generally used in wear surfaces, depending on the application whether they are permissible.
In metal matrix components, pores are also often found to form molten carbides through the influence of carbon.
The alloy is a percentage of the amount of the element melted and mixed in the surface treatment material. In for example the nickel coating for construction steel 10% iron (10% alloy), then the iron has come from the base material and thus affects the surface coating properties.
Laser cladding applications
Gas and steam turbine wings, boiler walls and heaters, valves, bases and sealing surfaces, cuttings.
Valve body and sealing surfaces, sealing collars, pump housings, impellers, flanges.
Pulper blades, crusher blades, rollers, hydraulic hammer arms, bearing housings.
Wires, thread guides, extrusion tools.
Crusher teeth, parts for oil rigs, cones, earth moving parts for example pins, piston rods, wheel hubs, etc.
Valves, cylinder tubes, piston rods, piston rings, shafts
Tools and dies, shaft seal and bearing surfaces, crankshafts, hydraulic pistons and cylinders, electric motor shaft cranks, blades.