| Synchronous powder feeding laser cladding technology has the advantages of high manufacturing efficiency,low shape limitation and good automation.It is receiving more and more attention in the field of metal parts failure repair.However,this technical material wastes a lot,and therefore,the production cost is often reduced in the production by reusing the residual powder with the new powder.However,under the influence of external factors such as laser heat treatment and air oxidation,the raw material powder is prone to changes in characteristics such as morphology,composition and fluidity,thus affecting the quality of repair.Based on the multi-wheel powder cycle laser cladding repair using GH4169 powder,the characteristics of the powder during the cycle and the effect of using recycled powder on the microstructure and properties of the cladding repair layer were analyzed.Based on the analysis of the impact mechanism,the process optimization was explored1.During the recycling process,the average particle size of the alloy powder increases,and the particle size distribution gradually concentrates from the dispersion.After several rounds of circulation,the amount of powder on the surface of the powder adheres to the satellite powder,and at the same time,it has a condensed molten pool metal to roughen the surface.Compared with the new powder,the bulk density and tap density of the powder after several cycles have decreased.The angle of repose,the angle of collapse,and the size of the flat angle increased slightly,and the overall fluidity of the powder decreased.During the cycle,a small amount of magnetic impurity powder is formed due to laser heat and oxidation.After a limited number of cycles,the content of the powder element is kept within the standard range,and the internal structure of the powder is not seriously damaged2.As the number of powder cycles increases,the energy input increases due to the change of powder morphology,and the columnar crystal proportion at the interface increases and the grain coarsening inside the structure occurs.At the same time,due to the increase in the content of Nb in the powder,it was found that the amount of Laves phase precipitation increased and the volume increased.An attempt to improve the precipitation of the Laves phase was carried out using a two-stage aging heat treatment,and it was found that the improvement effect was poor in the sample prepared using the recycled powder.3.The mechanical properties of Vickers hardness,tensile strength,flexural strength,anti-friction wear and erosion wear of powder-clad repair samples with different cycle times were tested and compared.The results showed that the Vickers hardness,tensile strength and flexural strength of the Cladding repair samples decreased with the increase of the number of powder cycles,and the plasticity of the samples deteriorated and the grinding loss increased.4.The process has been optimized and improved for the problem of using recycled powder to cause the performance of the cladding to repair the structure.The process parameters with better results were screened out.The powders were used as raw materials,and the repaired samples were prepared with optimized parameters.The mechanical properties such as tensile,bending and anti-friction wear were tested.The results show that the optimization of process parameters brings about a certain degree of improvement,and the mechanical properties of the samples are improved to some extent. |
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