Laser cladding is a new weld surfacing technology involving the deposition of any weldable material on the surface of a metal substrate using a laser beam. This technique can be used on both new and worn products and is typically used to weld rebuilt worn or damaged surfaces, hard-face wear-susceptible materials or weld-clad surfaces susceptible to corrosion, oxidation, wear or a combination of these. This flexible technique allows welding consumables to be deposited in either powder or wire form. Weld deposits are fully fusion-joined to the substrate material in thicknesses ranging from 0.1 to several millimeters - multiple layers can also be deposited. The very low heat-input rate associated with laser welding results in extremely low dilution with the substrate, also resulting in relatively small heat-affected zones (HAZ) and minimal distortion.

Many techniques are currently used in industry to repair and restore damaged/worn surfaces of high value components. Some of these long-standing practices are being phased out due to the inherent environmental problems they produce. Chrome plating is no longer acceptable due to its environmental restrictions. Conventionally cladding the damaged surface also has drawbacks and restrictions depending on component, use, and specifications. Conventional cladding requires high heat input which often leads to part distortion and material malformation. This process also involves pre-machining of the surface so that a layer of weld can be applied and machined to the original specifications of the component.

The laser cladding method uses low heat input which eliminates residual stress and distortion problems. By providing a true metallurgical bond with the parent material of the component being repaired, laser cladding produces minimal material malformation between the filler material and substrate of the component. This technology has been successful on filler materials, substrates, and lasers.

A LASER (Light Amplification by Stimulated Emission of Radiation) is an optical source that emits photons in a coherent beam. Laser light is typically near-monochromatic, i.e. consisting of a single wavelength or hue, and emitted in a narrow beam. This is in contrast to common light sources, such as the incandescent light bulb, which emit incoherent photons in almost all directions, usually over a wide spectrum of wavelengths.

Laser Cladding Benefits

The goal of cladding is to deposit a material of desired physical properties over a substrate. Cladding materials are chosen based on whether they need to provide corrosion resistance, wear resistance or higher hardness, depending upon the use of the base part being clad.

Once the physical properties of the application are determined and a cladding material is selected, the process to clad them needs to be decided upon. The cladding method can impact the performance of the cladding material. This is where the benefits in laser cladding over conventional cladding (MIG, TIG, thermal spray) start to show.

Laser cladding provides a strong metallurgical bond with minimal dilution of the base material. This is done with minimal heat input which also results in a small heat affected zone. Laser cladding also has better thickness control and as-clad surface finish than conventional cladding methods.

Dilution is defined as the amount of intermixing of the clad and substrate. Low dilution means there is very little of the base material mixing in with the clad, leaving a surface layer of cladding that is very close to the pure clad material. This results in material properties that are not compromised and the full affects of the clad can be achieved in one single layer.

There is a small zone of base material that does get melted in with the clad, and therefore creates a very good metallurgical bond, versus thermal spray types of cladding that are literally sprayed onto the surface and do not have a solid bond between the two layers.

A major benefit of laser cladding over conventional arc welding is that the thermal input can be precisely controlled, thus yielding minimal dilution and a small heat affected zone. This lower amount of heat input prevents distortion and the base material properties are not detrimentally affected.

The laser process is much more suitable for automation than conventional welding and, while conventional welding is limited to those in wire format, the laser process is compatible with all powdered metal materials, including ceramic.