Επένδυση με λέιζερ technology involves placing a selected cladding material onto the surface of a substrate using different filler methods. Through laser irradiation, a thin layer of the substrate surface melts and quickly solidifies, forming a metallurgically bonded surface coating with very low dilution. This significantly enhances the substrate material’s surface properties such as wear resistance, corrosion resistance, heat resistance, oxidation resistance, and electrical properties.

Classifications of Laser Cladding

Based on the type of materials used and their coupling with the laser beam, common επένδυση με λέιζερ technologies can be divided into: coaxial powder laser cladding, off-axis powder laser cladding (also called lateral powder laser cladding), high-speed laser cladding (also called ultra-high-speed laser cladding), and high-speed wire laser cladding.

Ομοαξονική επένδυση λέιζερ σκόνης

Coaxial powder επένδυση με λέιζερ typically uses a semiconductor fiber laser and a disc-type gas-fed powder feeder. The cladding head employs a circular light spot scheme with a central light beam and powder fed around it or multiple powder streams. With a specially designed protective gas channel, the powder, light beam, and protective gas converge at a single point, where a molten pool is formed. As the cladding head moves relative to the workpiece, a cladding layer forms on the surface.

Πλεονεκτήματα της ομοαξονικής επικάλυψης με λέιζερ σκόνης:

High freedom and easy automation: The cladding layer quality remains consistent regardless of the direction of movement, making it highly adaptable to automation with industrial robots or multi-axis machines.

Good inert gas protection: The molten pool is shielded by inert gases, improving process stability.

Small molten pool, even heating, and good crack resistance: The uniform interaction between powder and light ensures better quality and durability of the cladded surface.

Επίστρωση λέιζερ σκόνης εκτός άξονα

Also known as lateral powder επένδυση με λέιζερ, this method uses a semiconductor or fiber laser with a gravity-fed powder feeder. The cladding head employs a rectangular light spot combined with lateral powder feeding. The alloy powder is delivered to the workpiece surface and melted by the laser beam, forming a molten pool.

Πλεονεκτήματα της επικάλυψης με λέιζερ σκόνης εκτός άξονα:

High material utilization: Powder is pre-deposited onto the surface before being melted by the laser, achieving material utilization rates above 95%.

High cladding efficiency: The rectangular beam allows for increased laser power and larger spot sizes, improving the cladding speed.

No inert gas consumption: This method does not consume inert gas, although it requires careful consideration of powder oxidation resistance.

Επένδυση με λέιζερ εξαιρετικά υψηλής ταχύτητας

This process employs a high-quality fiber laser and high-speed cladding heads to achieve extremely high cladding speeds (up to 200 m/min). The powder is pre-heated or fully melted before entering the molten pool, dramatically shortening the time needed for powder melting.

Πλεονεκτήματα της επικάλυψης με λέιζερ υπερ-υψηλής ταχύτητας:

High laser energy utilization: The laser beam efficiently heats the powder and workpiece, minimizing energy loss and maximizing the cladding efficiency.

Χαμηλός ρυθμός αραίωσης: With high cladding speeds and brief molten pool exposure times, the dilution rate of the cladding layer remains low.

Low surface roughness and crack resistance: The process minimizes defects in the cladded layer, ensuring high-quality results.

Επένδυση με λέιζερ υψηλής ταχύτητας

High-speed wire επένδυση με λέιζερ uses metal wire as the cladding material, which is fed into the laser beam. The metal wire is melted to form a molten pool, which solidifies to create the cladding layer.

Πλεονεκτήματα της επικάλυψης με λέιζερ υψηλής ταχύτητας:

Environmental benefits: The use of wire instead of powder eliminates splashing and metal dust, improving environmental performance.

High material utilization: The wire is fully melted, ensuring nearly 99% material utilization.

High cladding efficiency: The controlled energy input and fast cladding speed result in high material efficiency.

The Impact of Process Parameters on Cladding Effect

Επένδυση με λέιζερ parameters, including laser power, spot diameter, cladding speed, focus offset, powder feed rate, scanning speed, and preheating temperature, significantly affect the cladding layer’s dilution rate, crack formation, surface roughness, and the overall density of the cladded parts. Improper parameter settings can lead to poor metallurgical bonding between the cladding and substrate, impeding the formation of multi-layer channels.

Οι βασικές παράμετροι της διαδικασίας περιλαμβάνουν:

Ισχύς λέιζερ: This determines the molten volume of the substrate. Increasing power leads to deeper cladding but also increases the likelihood of porosity. However, higher power can reduce cracks and porosity by improving dynamic solidification during the cooling phase.

Spot Diameter: The spot diameter of the laser affects the width of the cladding layer. While small spot sizes provide better quality, large spots are better for covering larger areas.

Cladding Speed: Cladding speed impacts how well the alloy powder melts. If too high, the powder won’t fully melt; if too low, the pool will overheat, leading to material loss.

Features of Laser Cladding Surface Formation Technology

Fast cooling speed and rapid solidification.

Low thermal deformation, with low dilution rates and excellent metallurgical bonding between the coating and substrate.

Wide material selection: Iron-based, nickel-based, copper-based, titanium-based, and more.

Precise thickness control: Cladding thickness ranges from 0.2mm to 2mm, ideal for wear part restoration.

High processing precision, suitable for small or hard-to-process areas.

Easy automation integration.

Laser Cladding Material Systems

The choice of cladding materials is crucial to achieving the desired surface quality and properties. Typically, the selection of appropriate materials depends on the substrate’s physical and chemical properties, and the cladding material must be chosen accordingly.

Material Systems:

Self-Fusing Alloy Powders: These include iron-based, nickel-based, and cobalt-based powders and are most commonly used in laser cladding. They offer excellent corrosion and oxidation resistance.

Composite Powders: These combine high-melting-point ceramics such as carbides, nitrides, and borides with metals, forming powders ideal for producing wear-resistant coatings.

Ceramic Powders: Including oxide-based ceramics like aluminum oxide and zirconium oxide, these are commonly used for producing heat-resistant coatings.

Other Alloy Powders: Copper-based, titanium-based, aluminum-based, and other specialized alloy powders are also used depending on the application requirements.

Συμπέρασμα

Επένδυση με λέιζερ technology is widely used in industries like aerospace, automotive, petrochemical, metallurgy, and rail transportation to repair and enhance critical components. By providing a cost-effective solution for repairing damaged parts, επένδυση με λέιζερ reduces costs, boosts efficiency, and enhances performance. With advancements in high-power lasers and reduced manufacturing costs, επένδυση με λέιζερ is becoming a hot topic in both academic and industrial research.