The term "laser" is an abbreviation of Light Amplification by Stimulated Emission of Radiation. The wide application of lasers is due to their ability to act as a medium for communication, photography, and medical applications as well as their ability to evaporate materials at the atomic level. Several types of lasers are used in manufacturing operations, but the most common are CO2 (gas) and Nd:YAG (solid-state) lasers, named after the molecule or atom producing the laser light. Lasers can be used for welding, cutting, drilling, surface transformation hardening, surface melting and surface cladding. Laser cladding involves fusing an alloy addition to produce a metallurgically-bonded surface with improved wear, friction and/or corrosion performance. The deposition process involves the spraying of a coating material, either a powder or a wire, to the laser beam traversing on the surface of the material or component to be coated. The powder and a thin surface layer of the material to be coated are heated by the laser beam. This allows them to "melt" sufficiently and fuse together, forming a real metallurgical bonding between the coating and the base material. The powder feeding is performed through either co-axial or off-axial powder nozzles. Using off-axial nozzles, a group of institutes and manufacturing research centres have optimised a powder delivery system for laser cladding. An important feature of this feeding device is the integrated on-line feeding rate measurement and control system. The measuring principle is based on the continuous recording of the weight of the powder feeder during the feeding process using a special balance integrated into the feeding device. Therefore, the actual powder mass flow rate can be calculated as weight loss per time unit. A special coaxial nozzle for powder delivery was also designed, built and tested The development of this coaxial cladding nozzle for multi-kW fibre coupled YAG laser is a major step forward because, compared to the coaxial nozzle for CO2 lasers, the energy coupling rate is twice as good. In addition, compared to the lateral nozzle the powder efficiency is more than 90% instead of a maximum 65%, which means consumable cost savings. Moreover, the coaxial nozzle allows multidirectional cladding opening new trails for new applications such as the repairing of complex shapes. Advanced beam-shaping modules for mid-range power laser diodes were also designed. Power diode lasers were introduced fairly recently, representing the newest generation of power lasers for material processing. The designed modules allow the optimisation of the beam shape in accordance to the process specification and the use of optical fibres to monitor the process on-line.
Discover other articles in the same domain of application
Network of Science, Companies and Politics for the Research and Development of Bio-based Plastics Gets Underway
30 June 2020