Copper and its alloys have been widely used in many fields such as electronics, electrical engineering, and mechanical manufacturing due to their good electrical conductivity, thermal conductivity, and corrosion resistance. However, during long-term use, the copper surface may be damaged due to wear, corrosion, scratches, etc., affecting its performance and service life. Laser cladding technology, as an advanced surface repair technology, provides an effective solution for the repair of copper surfaces. This article will introduce in detail how to use laser cladding technology to repair copper surfaces and matters that need to be paid attention to.
1. Principle and process of laser cladding technology for repairing copper surface
(I) Principle
Laser cladding technology uses a high-energy laser beam as a heat source to quickly melt the cladding material pre-coated or synchronously delivered to the copper surface, so that it forms a good metallurgical bond with the copper substrate surface, thereby forming a cladding layer with specific properties on the copper surface to repair the copper surface damage.
(II) Process
(1). Preparation before repair
– Detect and evaluate the damage on the copper surface to determine the type, degree and scope of the damage.
– Clean the copper surface to remove pollutants such as oil, rust, and oxide layer to ensure good bonding between the cladding layer and the substrate.
– Select appropriate cladding materials according to the damage and repair requirements.
(2). Selection and preparation of cladding materials
– The selection of cladding materials should take into account factors such as compatibility with the copper substrate, matching of thermal expansion coefficient, wear resistance, and corrosion resistance. Commonly used cladding materials include nickel-based alloys, cobalt-based alloys, copper-based alloys, etc.
– The cladding material can be in powder form and added to the copper surface by airborne powder delivery, pre-set powder, etc.
(3). Determination of laser cladding process parameters
– Laser power, scanning speed, spot diameter, powder delivery speed, overlap rate and other process parameters have an important impact on the quality and performance of the cladding layer. It is necessary to determine the appropriate process parameters through experiments and optimization.
(4). Laser cladding repair
– Fix the prepared copper workpiece on the workbench and adjust the distance and angle between the laser head and the copper surface.
– According to the determined process parameters, start the laser equipment for cladding repair. During the cladding process, the quality and temperature of the cladding layer should be monitored in real time, and the process parameters should be adjusted in time.
(5). Post-repair treatment
– After the laser cladding repair is completed, the repaired copper surface is subjected to stress relief annealing to eliminate residual stress and prevent deformation and cracking.
– The cladding layer is subjected to mechanical processing, grinding, polishing and other treatments to meet the design size and surface accuracy requirements.
2. Matters needing attention when repairing copper surfaces with laser cladding technology
(I) Energy absorption problem
Copper has a high reflectivity to lasers, resulting in a low absorption rate of laser energy. In order to improve energy absorption, the copper surface can be pretreated, such as sandblasting, phosphating, blackening, etc., to increase surface roughness and absorption rate; or an appropriate amount of absorbent, such as carbon powder, graphite powder, etc., can be added to the cladding material.
(II) Thermal conductivity problem
Copper has a high thermal conductivity. During the laser cladding process, heat is easily dissipated quickly, making it difficult to maintain the temperature of the molten pool, affecting the formation and quality of the cladding layer. Therefore, it is necessary to appropriately increase the laser power and reduce the scanning speed to increase the heat input; at the same time, the preheating method can be used to increase the initial temperature of the copper substrate and reduce heat loss.
(III) Crack problem
Due to the large difference in the thermal expansion coefficients of copper and the cladding material, thermal stress is easily generated during the cladding process, resulting in cracks in the cladding layer. In order to reduce the occurrence of cracks, you can choose a cladding material with a thermal expansion coefficient similar to that of the copper substrate; or use a multi-layer cladding method to gradually transition and reduce thermal stress; in addition, proper post-heat treatment can also effectively eliminate residual stress and reduce the occurrence of cracks.
(IV) Oxidation problem
During the laser cladding process, the copper surface easily reacts with oxygen in the air to form an oxide layer, which affects the bonding between the cladding layer and the substrate. Therefore, it is necessary to use inert gas protection during the cladding process, such as argon and nitrogen, to prevent oxidation of the copper surface.
(V) Process parameter optimization problem
Laser cladding process parameters have a vital impact on the quality and performance of the cladding layer. When repairing the copper surface, it is necessary to determine the optimal process parameters through a large number of experiments and optimizations based on factors such as the characteristics of copper, the properties of the cladding material, and the damage to obtain a high-quality cladding layer.
Laser cladding technology provides an efficient, precise and reliable method for repairing copper surfaces. By reasonably selecting cladding materials, optimizing process parameters, and paying attention to relevant matters, the damage on the copper surface can be effectively repaired and its performance and service life can be improved. With the continuous development and improvement of laser cladding technology, it is believed that its application in the field of copper surface repair will become more and more extensive, providing strong support for the development of related industries.
