Research On Laser Cladding Forming Of Ternary Twisted Blade With Special-Shaped Base Surface

Ternary twisted blades are mostly found in the impellers of aerospace engines,marine gas turbines and centrifugal compressors.Such blades have complex structural characteristics such as large inclination and large twist.The blade thickness is thin and the distance between the flow channels is narrow.At present,it is mainly processed by technologies such as CNC EDM,CNC milling,precision blanking and precision welding.The material removal during the processing is large and the processing cycle is long.Laser cladding forming is a new type of metal additive manufacturing technology,which has the advantages of no mold,high efficiency,complex forming parts,and excellent comprehensive performance.This paper studies the existing difficulties in the experimental process of laser cladding forming ternary twisted blades.In this paper,the "light internal powder feeding" nozzle independently developed by the laboratory is used.First,the copper powder spraying tube commonly used in the laboratory in the nozzle is improved,and the composite powder spraying tube is used to reduce the divergence angle of the powder beam and improve the powder utilization rate.The principle of laser internal powder feeding defocusing cladding nozzle to realize hollow annular spot is expounded,and the energy distribution model of hollow inverted cone laser beam under negative defocusing is established.The energy distribution of annular spot scanning is saddle-shaped,which is more suitable for cladding take shape.In order to reduce the offset of the curved molten pool,the height of the cladding layer should be reduced.Therefore,the scanning rate of the cladding nozzle should be appropriately increased during cladding to reduce the amount of laser and powder.The number of couplings per unit time,so that the molten pool solidifies at a faster rate.The lift model of the cladding nozzle is established,and the mathematical relationship between the lift of the nozzle and the actual deposition height is obtained.When the lift is calculated to be 2/3 of the actual deposition height of the cladding channel,the single surface of the surface can be continuously clad,and the two sides of the blade can be continuously clad.The roughness is low,which effectively alleviates the step effect.The forming functions of different section heights of the surface melt channel are established,and the scanning rates of different areas of the ternary twisted blade are calculated to achieve a smooth transition of blade heights,and the forming quality of the blade area with different heights is better.The reasons for cracking of the surface melt channel and the matrix were analyzed.By preheating the matrix to 400℃ and keeping it warm during the experiment,the cracking problem during the forming process was effectively solved.Aiming at the thin-walled structure characteristics of the ternary twisted blade with large inclination and large torsion,a streamline layering is proposed on the curved substrate,and the tangent plane slice along the radial arc of the main base is adopted,and then a single cladding layer is divided into several equal parts.Each division unit is divided,and the spatial angle and position of each division unit when cladding are calculated,these parameter information is imported into the motion system,and the KUKA teach pendant is used to associate the system tool coordinate system with the coordinate system set by the streamline layering.,the running path of the KUKA robot arm during cladding can be obtained,and then the corresponding cladding process is matched according to the different characteristics of different areas of the blade to complete the cladding forming of the ternary twisted blade and the impeller.The ternary twisted blade is tested:the average surface roughness of the formed part is within 4.065 μm,and the roughness is low;the average thickness of the blade is 5.97 mm,the relative error of size is-1.4%～1.03%,and the error of torsion angle is-4.67%,the forming accuracy is high;with the increase of the height of the formed part,the heat accumulation at the laser molten pool is obvious,the microhardness decreases slightly,the microstructure increases slightly,and the microhardness of the formed part is between 348.3～360.4 HV,The metallographic structure is dense and uniform as a whole,without obvious holes or crack defects.