Research On The Rapid Manufacturing Of Thin-walled Part With Unsmooth Transition By Coaxial Inside-beam Powder Feeding

Laser Cladding Forming (LCF) technology, which mixes the advantages of LaserCladding and Rapid Forming technology, has become one of the important researchdirections of advanced manufacturing technology. At present, the main method ofpowder seeding in LCF is outside-beam powder seeding technology, which contains twokinds of classifications called lateral powder feeding and coaxial powder feeding. Thereare many problems arising when the two methods are used, such as the laser beam can’tmatch the metal powder well, the part’s surface is too rough, the utilization efficienciesof energy and powder are very low and so on.According to the shortcomings of lateral outside-beam and coaxial outside-beampowder feeding, our research group has developed a kind of new technology calledcoaxial inside-beam powder feeding, which can solve all the problems above. By seriesof experiments, this paper analyzed the relationship of energy and the relationshipsmetal powder, and summarized the parameters’ influence to the layer’s feature andquanlity (The parameters contain laser power, powder seeding velocity, scanningvelocity, defocusing distance.).At last some cladding experiments were made to aquirethe layers with variable width. The experiment results can be showed as follow:(1)When the laser power is very low, the layer’s height and width become larger with laserpower’s increase.When the laser power is high enough,it has little effect on the layer’sheight and width.(2) When the powder seeding velocity is very low, the layer’s heightand width become larger with the powder seeding velocity’s increase.When the powderseeding velocity is high enough,it has little influence on the layer’s height and width.(3)When the scanning velocity increases, the cladding layer’s height decrease evidently,and it’s width slightly.(4) When the powder seeding nozzle is in the minus defocusingstate, as the defocusing amount increases, the cladding layer’s height increases, and thewidth decreases.When the powder seeding nozzle is in the plus defocusing state, as the defocusing amount increases, the cladding layer’s height decreases, and the widthincreases.Although the coaxial inside-beam powder feeding technology is better than the oldmethods, it has been not yet a mature technology. According to the existing weaknessesof coaxial inside-beam nozzle and the adjusting device in the process of laser cladding,this paper has made some modifications in the design of them.Taking the square thin-walled part’s forming processing for an example, this paperused the conventional LCF technology to manufacture thin-walled part with unsmoothtransition.The results showed that there were steady bulges appeared in the square’scorners, which made the experiment can’t be carried out smoothly. According to thissituation, this paper firstly put forward the auto-repairing theory in the formingexperiment of thin-walled part with unsmooth transition. This paper modificated theexperiment scheme by the auto-repairing theory.According to this theory above,thispaper improved the test scheme from two aspects:(1) Instead the single-axis scanningmode with X, Y linkage scanning mode.(2) Instead the plus defocusing state withminus defocusing state.At last,we got square thin-walled part successfully.The testing and analysis of the part showed that the microstructure was uniformlydistributed, and the part’s hardness was higher than the castings and the ordinary steelparts with heat treatment. This experiment has a certain significance to the formingexperiment of thin-walled part with complex structure in the future.