In modern industrial production, many metal materials are widely used due to their good physical and chemical properties. However, some of these materials, such as aluminum, copper and their alloys, have high reflectivity, which brings challenges to surface repair. As an advanced surface repair technology, laser cladding technology has great potential in repairing the surface of highly reflective substrates. This article will discuss in detail how laser cladding can repair the surface of highly reflective substrates.

1. Characteristics of high-reflective substrates and repair difficulties

• High reflective characteristics
  Highly reflective substrates such as aluminum and copper have high reflectivity to lasers, which makes the absorption rate of laser energy on the surface low. This means that when performing laser cladding, higher laser power or special measures are required to increase energy absorption to achieve melting of the substrate surface and deposition of cladding materials.
• High thermal conductivity
  Highly reflective substrates usually have high thermal conductivity, and the heat generated by laser irradiation is easily conducted and dissipated quickly, making it difficult to maintain the temperature of the molten pool, affecting the formation and quality of the cladding layer.
• Easy to oxidize
  Metals such as aluminum and copper easily react with oxygen in the air at high temperatures to form an oxide film. The presence of an oxide film will hinder the absorption of laser energy and the combination of cladding materials and substrates, reducing the repair effect.

2. Technical strategies for laser cladding to repair the surface of highly reflective substrates

• Laser parameter optimization
  By adjusting parameters such as laser power, scanning speed, and spot diameter, the absorption rate and utilization rate of laser energy on the surface of highly reflective substrates can be improved. For example, appropriately increasing the laser power, reducing the scanning speed and the spot diameter can increase the energy input per unit area, which helps to improve the cladding effect.
• Surface pretreatment
  Before laser cladding, pretreatment of the surface of the highly reflective substrate is an important measure to improve the repair effect. Common pretreatment methods include sandblasting, pickling, phosphating, etc. These methods can remove the oxide film and pollutants on the surface, increase the surface roughness, and improve the absorption rate of laser energy and the adhesion of the cladding material.
• Adding absorbent
  Adding a certain amount of absorbent, such as carbon powder, graphite powder, etc., to the cladding material can improve the absorption capacity of the cladding layer to the laser. The absorbent heats up rapidly under the action of the laser, transfers energy to the cladding material and the substrate, and promotes melting and bonding.
• Preheating treatment
  Preheating the highly reflective substrate can reduce the influence of thermal conductivity and increase the temperature and stability of the molten pool. The preheating temperature and time need to be reasonably selected according to the characteristics of the substrate and the repair requirements. The general preheating temperature is between 100-300℃.
• Selecting the right cladding material
  Choosing a cladding material with good compatibility and similar thermal expansion coefficient with the highly reflective substrate can reduce the generation of thermal stress and cracks. At the same time, the melting point, fluidity, wettability and other properties of the cladding material will also affect the repair effect, which needs to be considered comprehensively.

3. Application cases of laser cladding to repair the surface of highly reflective substrates

3.1 Surface repair of aluminum alloys

Aluminum alloys are widely used in aerospace, automobile manufacturing and other fields, but due to their high surface reflectivity and high thermal conductivity, they are prone to wear and corrosion. Using laser cladding technology, selecting appropriate cladding materials and process parameters to repair the worn or corroded aluminum alloy surface can significantly improve its surface performance and service life. For example, in the repair of aluminum alloy blades of aircraft engines, the hardness, wear resistance and corrosion resistance of the repaired blade surface have been significantly improved by laser cladding of cobalt-based alloy powder.

3.2 Surface repair of copper alloys

Copper alloys have important applications in electronics, electrical, and mechanical manufacturing, but due to their high surface reflectivity and easy oxidation, they are prone to wear and scratches during use. Laser cladding technology can be used to clad nickel-based alloy or cobalt-based alloy powder on the surface of copper alloy, which can effectively repair surface damage and improve its surface performance and reliability. For example, in the manufacture of printed circuit boards, laser cladding technology can be used to repair the worn copper alloy mold surface, extending the mold’s service life and improving production efficiency.

Laser cladding technology has unique advantages and potential in repairing highly reflective substrate surfaces. Through technical strategies such as optimizing laser parameters, surface pretreatment, adding absorbents, preheating, and selecting suitable cladding materials, energy absorption, heat conduction, oxidation, and other problems in the process of surface repair of highly reflective substrates can be effectively solved, and the repair effect and quality can be improved. With the continuous development and improvement of laser cladding technology, it is believed that its application in the field of surface repair of highly reflective substrates will become more and more extensive, providing more efficient and reliable solutions for surface repair in industrial production.