Research On Mechanism And Process Of Laser Cladding Rapid Manufacturing Using Coaxial Inside-Beam Powder Feeding

For the disadvantages of the lateral powder feeding and multi-lateral coaxial powder feeding process in laser cladding rapid prototyping process, a new process of hollow focusing laser, powder tube being medial and inside-beem powder feeding is put forward, which can be especially apply in laser cladding direct manufacturing.The major work completed and the results obtained are as follows:1.A new system of inside-beam coaxial powder feeding is designed, which can transform the conical focusing laser beam to hollow conical focusing laser beam and powder is delivered to the middle hollow part, and powder is coaxial with the laser. Then the performance of this system is analyzed. The results show that the powder utilization can reach to 60% -75%, which is 50 percent higher than that of the existing coaxial powder.2. Selecting the overall regional powder as the research object, the simplified mathematics model of powder shading efficiency and powder temperature increment model is established, and the power effect efficiency is analyzed also, which is useful for the design and optimization of powder feed nozzle and the simulation of forming process.3. The key process parameters, such as laser power density, beam of light mode and scanning speed etc, are studied in detail. In the multimode laser, the relation between different process parameters and cladding coat quality is found out, which can prepare fully for shaping multilayer parts.4. The finite element analysis model of temperature and stress of the laser cladding rapid manufacturing using inside-beam powder feeding is established, temperature distribution and the stress distribution of the workpiece is researched, which is theoretically useful for controlling the quality of microstructure and to prevent the cracks. Then the pool temperature control system is designed that can prevent heat accumulation effectively and delay cracks remarkably.5. Based on the theoretical analysis and experimental research, the laser cladding rapid manufacturing using inside-beam powder feeding is developed. The applications in the typical metal parts with process of variable direction, variable cross-section and variable spot are studied. Combined with laser re-melting, a better surface quality can be obtained.The results show that if adopting the system of the laser cladding rapid manufacturing using inside-beam powder feeding, the powder utilization and forming quality can be improved; compared with the original mode, there has a dense microstructure and no more defects, the process is more stable and reliable, the surface roughness is reduced greatly, and there is no "the thick top and the thin bottom " phenomenon, and has no melting particles in the side wall.