LASER CLADDING TECHNOLOGY
- 1 LASER CLADDING TECHNOLOGY
- 1.1 Working of Laser Cladding:
- 1.2 Materials
Laser Cladding is the process wherein the metal (powder/wire) is deposited on to another metal using a laser as heat source. It’s an alternative to traditional welding and thermal spray. Laser cladding, also known as laser metal deposition, is a technique for adding one material to the surface of another. Laser cladding involves the feeding of a stream of metallic powder or wire into a melt pool that is generated by a laser beam as it scans across the target surface, depositing a coating of the chosen material.
Laser cladding technology allows materials to be deposited accurately, selectively and with minimal heat input into the underlying substrate. The laser cladding process allows for property improvements for the surface of a part, including better wear resistance, as well as allowing for the repair of damaged or worn surfaces. Creating this mechanical bond between the base material and the layer is one of the most precise welding processes available.
This technology is similar to thermal spray in that it has an energy source to melt the feed stock that is being applied to a substrate. Where it differs is that it uses a concentrated laser beam as the heat source and it melts the substrate that the feed stock is being applied to. This results in a metallurgical bond that has superior bond strength over thermal spray. Additionally the resulting coating is 100% dense with no voids or porosity.
Working of Laser Cladding:
The basic system is made up of a laser to generate the beam, a set of optics to direct and focus the beam, a powder feeder, and a part manipulator. The laser and optics stay stationary and the part is moved in relationship to the laser. The laser cladding systems are fully automated providing precise control of the coating (cladding) process.
Laser Cladding Process Basics
|Typical laser power||1 – 6 kW|
|Typical build up rate||0.1 to 12 kg|
|Typical coating thickness||0.2 to 4 mm (or more)|
|Coating materials||Weldable powders (metals, metallic alloys, carbide blends)|
Key characteristics of Laser Cladding Technology
- Perfect metallurgically bonded and fully dense coatings
- Minimal heat affected zone and low dilution between the substrate and filler material resulting in functional coatings that perform at reduced thickness, so fewer layers are applied
- Fine, homogeneous microstructure resulting from the rapid solidification rate that promotes wear resistance of carbide coatings
- Edge geometries can be coated and built up with welded deposits
- Near net-shape weld build-up requires little finishing effort
- Extended weldability of sensitive materials like carbon-rich steels or nickel-based super alloys that are difficult or even impossible to weld using conventional welding processes
- Post-weld heat treatment is often eliminated as the small heat affected zone minimizes component stress
- Excellent process stability and reproducibility because it is numerical controlled welding process
Laser cladding can be performed with a variety of metals including:
- Aluminium alloys (Al-(Mg)-Si)
- Cobalt alloys (Co, C, Cr, W)
- Copper alloys
- Nickel self-fluxing alloys (Ni-Cr-B-Si)
- Stainless steels (Fe, Cr, Ni)
- Super alloys (Ni, Co, Mo, Cr, Si)
- Titanium alloys4
- Tool steels (Fe, C, Cr, V)
- MMC including carbides (WC, TiC, CBN)
- Nano additive alloys (oxide dispersion strengthened alloys)
This wide range of materials means that laser cladding can be used for a large selection of industrial applications, including rapid manufacture, repair of parts, and surface enhancement. Materials such as tungsten carbide in a MMC, for example, offers durability making it ideal for coating applications that require superior wear resistance.
Advantages of Laser cladding Technology:
One of the advantages of the laser cladding process is the concentrated beam of energy from the laser. It can be focused and concentrated to a very small area and keeps the heat effected zone of the substrate very shallow. This minimizes the chance of cracking, distorting, or changing the metallurgy of the substrate. Additionally the lower total heat minimizes the dilution of the coating with material from the substrate.
Coating thicknesses can reach .125″ (3.1mm) with carbides in one pass and can go to any thickness with other materials and multiple passes.
Because the feed stock is a powder, so there is a large variety of materials available including pure metals, alloys, or carbides. Further the development extensively with Inconel and Stellite alloys on a wide assortment of oil field applications.
Applications of laser cladding technology:
- Optimal Part Design by Dissimilar Metal Deposition
- Ideal for Repair & Restoration
- Material Research & Development
- Wear Resistance & Fatigue Life Improvements
Laser clad materials can be used as layers to protect saw blades, counter blades, disc harrows and other cutting tools from wear and corrosion, while providing superior cutting characteristics. The lack of distortion with this process means that these tools are kept straight while different coating thicknesses can be achieved to suit requirements. These coated tools can find applications across industry, including construction and agriculture.
High performance drilling tools are used in a range of industries including oil and gas, mining, and geothermal. These tools need wear protection to withstand the stresses they are subjected to and reach their required lifetimes. Laser cladding is becoming increasingly common as a technique for applying coatings due to the materials performance this process provides.
Heat exchangers can suffer corrosion from the corrosive liquids and gases that they come into contact with. Laser cladding with coatings such as nickel alloys with good corrosion resistance and toughness can help avoid cracking in heat exchangers, while also offering improved wear protection even at high temperatures.
Hydraulic cylinders, such as those used in the mining industry, require coating in order to mitigate against the corrosion caused by the local atmosphere. Chrome plating was the primary method used in the past, but this is increasingly being superseded by laser cladding, due to the superior durability it offers. Some estimates say that laser cladding can improve durability of these products by 100%.
Replacement for Hard Chromium Plating
Hard chromium plating has been facing prohibitive measures from the EU, leading the industry to try and seek alternative solutions. Laser cladding had been discounted as a solution in the past because it wasn’t deemed fast enough or able to deliver thin enough coatings. However, developments in the technology (specifically, extreme high-speed laser application) now allow for higher speed deposition with thinner layers in a more power efficient manner, meaning that laser cladding can provide an effective alternative to hard chromium plating for particular applications.