Study On Laser Wire-melting Deposition Technology

Laser Wire-Melting Deposition(LWMD)is a new rapid prototyping technology. Based on the principle of layered-stack, the wire melting by laser was deposited, and then a 3 dimension part whose density is nearly 100% was manufactured.It has been researched in depth by foreign scholars, but only a few domestic colleges and universities had done some basic research on the technology, and few study was done on the microstructure and mechanical properties of the forming part.In this paper, the technological characters of LWMD were studied with the filling material of 316 l stainless steel. Then, the optimization of process parameters was finished. On the basis of this, the microstructure and mechanical properties of the multilayered parts created by LWMD were analyzed.Firstly, the process parameters of the single cladding were studied and optimized. Through the single factor experiment.It was found that the best cladding was obtained by front feeding and placing the wire at the center of the melt pool. For the process window of the single cladding investigated in this work, the optimal levels were 2000~2800w for laser power, 0.27 ~0.54m/min for cladding speed, and 2.0 ~3.2m/min for wire feed rate. I n the interval, the change of the single cladding's width and height was slow, which was helpful to improve the forming precision. It was found that the dilution ratio, aspect ratio and grain dimensions in the center of the cladding increase with increasing line energy.Then,the forming precision, microstructure and mechanical properties of the single bead walls were researched by the Taguchi experimental.it was shown that the laser power and cladding speed are the dominating factors with the main significant influence on the forming precision and hardness,but the cladding speed has the greatest influence on the fluctuation magnitude of the hardness. For the process window investigated in this work, the optimal levels were less than 400J/mm for the line energy, less than 550J/mm for laser energy per unit volume of wire, with the high quality of the single bead walls. Besides, it was found that the uniformity of the microstructure became worse with the increasing of line energy. The tensile properties also showed dependence on the direction of the test carried out. Tensile properties of the sample along the scanning direction were better than the sample across the scanning direction. All the examined tensile properties of the as deposited samples matched properties of the as cast material.Finally, under the optimization of processing parameters, the microstructure and mechanical properties of the multilayered parts would be studied after the experiment of appropriate overlapping rate. The results displayed that the best cladding could be contained when the overlapping rate was 0.05 higher than the critical overlapping rate. A band region was observed between two deposited layers, and the grain dimensions of the band were smaller. Otherwise, the average hardness of the overlapping area and non-overlapping area was almost same, while the average hardness of the remelting area was slightly higher than the non-remleting area's. The tensile strength gradually increased from the top to bottom of the forming parts.Tensile properties of the sample along the scanning direction was better than the sample across the scanning direction. All the examined tensile properties of the as deposited samples matched properties of the as cast and wrought material.