Month: June 2020

Laser Cladding Technology | The Latest Trend In Laser Cladding Process | Laser Cladding Applications | 5 Common Myths About Laser Welding | Laser Cutting | Laser Cladding Repair Services

  LASER CLADDING TECHNOLOGY

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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.

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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:

01-schematic diagram of Laser_Cladding_System_setup

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.

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Laser Cladding Process Basics

Typical laser power1 – 6 kW
Typical build up rate0.1 to 12 kg
Typical coating thickness0.2 to 4 mm (or more)
Coating materialsWeldable 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

Materials

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
  • Cutting Tools

    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.

  • Drilling Tools

    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

    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

    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.

Carbon Fibre Reinforced Plastics | Carbon Fibre Reinforced Polymers Use | 5 Reasons Why CFRP Applications Is Getting More Popular In The Past Decade

Carbon Fibre Reinforced Plastics

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The Composite’s properties are mainly influenced by the choice of fibers. Three types of fibres are Glass fibre, Carbon fibre, Aramid fibre. All fibres have generally higher stress capacity than ordinary steel and are linear elastic until failure. The most important properties that differ between the fibre types are stiffness and tensile strain.

Carbon fiber reinforced polymer (CFRP) is a type of composite materials consist of carbon fiber and polymer. The carbon fiber provides the strength and stiffness while the polymer acts as cohesive matrix to protect and held the fibers together. Carbon fibre reinforced plastics are manufactured as a strips, bars, and sheets using different production technique like filament winding, pultrusion, and hand lay-up processes.

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Carbon Fibre Reinforced Plastics Properties:

Composite materials, reinforced with carbon fibre, are different than other FRP composites using traditional materials such as fibreglass or aramid fibre. 

  • High Modulus of Elasticity 200 – 800 GPa.
  • Tensile Strength 2500 – 6000 MPa.
  • Density 1750 – 1950 Kg / m3.
  • Ultimate Elongation 0.3 – 2.5 %.
  • Carbon fibre reinforced plastics do not absorb water.
  • Carbon fibre reinforced plastics are resistant to many chemical solutions.
  • Carbon fibre reinforced plastics withstand fatigue excellently.
  • Carbon fibre reinforces plastics do not show any creep or relaxation.
  • Carbon fibre reinforced plastics is electrically conductive.
  • Light weight than other FRP composites
  • Increased strength than other FRP composites

What is Composites?

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When the fibre and the matrix are combined into a new material it becomes a composite. The fibres may be placed in one direction in the composites and then the composite is unidirectional. However fibres may also be woven or bonded in many directions and the composite becomes bi or multi directional.

How are carbon fibers produced?

Carbon fibers are the product of a high-tech manufacturing process. It starts with a starting product such as polyacrylonitrile (PAN). Polyacrylonitrile is a solid in the form of a white powder. It is hard and stiff as well as resistant to chemicals and solvents. In a first process step, thin threads are produced from it, which are then wound onto a spool – the so-called PAN “precursor” has been created.

In the next step, these threads are placed in the oven. First, they are oxidized at 200 to 300 degrees Celsius and then carbonized at 1200 to 1800 degrees Celsius. What remains are threads with a very high carbon content and high strength. After surface treatment and application of a sizing, the carbon fiber is wound up and is ready for use.

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Composite Manufacturing:

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  • Hand lay up method
  • Pultrusion method
  • Filament winding
  • Moulding

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Spinning, Stabilizing, Carbonizing, Surface Treatment and Sizing 

The manufacturing process for carbon fiber is partly chemical and partly mechanical.

  • Spinning:  The PAN is spun using one of a few spinning processes.  This step is important because it forms the internal atomic structure of the fiber.  The fibers are then washed and stretched to the required diameter.  The stretching also helps align the molecules to aid in the formation of the carbon crystals created by carbonization.
  • Stabilizing: In this step the fibers are treated with chemicals to change their linear bonding to a thermally stable ladder bonding structure.  The filaments are then heated in air so they pick up oxygen molecules and change their atomic bonding pattern.
  • Carbonizing: The fibers are then exposed to very high heat without oxygen present so the fiber cannot burn.  The atoms in the fiber vibrate violently expelling most of the non-carbon atoms in the precursor.  
  • Surface Treatment:  After carbonizing, the surface of the fibers does not bond well with the materials used in making composite materials.  In this step, the surface of the fibers are slightly oxidized by immersion in various gases or liquids.
  • Sizing:  In this process, the fibers are coated to protect them from damage during winding or weaving.

A few products made from carbon fibers are fishing rods, bicycles, golf equipment, tennis rackets, parts for aircraft’s, bridges, and automobiles. 

Manufacturing Methods for CFRP

  1. Continuous reinforcement process
  2. Filament winding
  3. Pultrusion
  4. Hand lay-up processes
  5. Moulding processes
  6. Matched-die moulding
  7. Autoclave moulding
  8. Vacuum bagging
  9. Resin injection processes
  10. Resin transfer moulding
  11. Reaction injection moulding

Carbon Fibre Reinforced Polymers (CFRP):

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CFRP is sometimes referred to as Carbon Fibre Reinforced Plastics is similar to fibre glass. Carbon fibre reinforced plastics is woven into a textile material and resin such as epoxy resin is applied and allowed to cure. The resulting material that is very strong as it has the best strength to weight ratio of all construction materials. It is an improvement on glass fibre reinforced plastic, although much more expensive.

Carbon Composite (CFRP) Friction Bearings:

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Friction bearings commonly use lubricating oil to separate the moving component from the mated non-moving bearing surface. Friction bearing surfaces commonly consist of a material that is softer than the supported component.

These friction bearings provide excellent dry running characteristics and can be used in operation after lubrication system failure making them an ideal solution for use in pumps and construction machinery as well as in mechanical engineering and shipbuilding or in offshore and onshore facilities to reduce maintenance and increase reliability. It can withstand up to 260 degree Celsius.

Real Life Applications of Reinforced Plastics (CFRP)

1. CFRP Strips

There are many techniques that use CFRP strips, laminates for strengthening concrete structures such as Externally bonded CFRP sheets and Near Surface Mounted FRP. The performance of the strengthening methods depends on the strength of the adhesive used to bond Carbon Fibre Reinforced Plastics to the concrete surface and the degree of stress at the interface of the concrete and Carbon Fibre Reinforced Plastics.

Carbon Fibre Reinforced Plastics is used to strengthen steel road bridges more easily and cheaply. The Carbon Fibre Reinforced Plastics strips are only 20% of the weight of the strips of similar products made from high-strength steel but are at least four times as strong. Their high-strength-to- weight ratio makes the CFRP strips easily to handle and reduces installation costs. Strips of Carbon Fibre Reinforced Plastics measuring just 8 mm in thickness have been used to strengthen a road bridge in Rochdale, UK.

01-CFRP laminates for structural strengthening

2. CFRP Wraps

CFRP wrapping is used for rehabilitation of masonry columns. Carbon Fibre Reinforced Plastics wraps are used for corrosion control and rehabilitation of reinforced concrete columns. They are also used for construction of earthquake resistant structures.

The addition of CFRP sheets greatly increases the ultimate flexural moment capacity of the retrofitted shear wall. However, in order for the FRP sheet to carry the high axial loads resulting from the bending moment imposed on the shear wall, the Carbon Fibre Reinforced Plastics sheets must be adequately anchored at the base of the wall.

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3. CFRP Laminates

Low Thermal Expansion CFRP Laminates are used for strengthening of structural members such as beams in buildings and girders in bridges. Carbon Fibre Reinforced Plastics is used to strengthen steel road bridges more quickly, cheaply and easily.

4. CFRP Bars

CFRP bars have been in the construction of new buildings and strengthening reinforced concrete structures using Near Surface mounted Carbon Fibre Reinforced Plastics Reinforcement technique.  

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