Numerical Simulation Of Molten Pool In Coaxial Powder-feed Laser Cladding

Laser cladding has a wide use in improving surface characteristic of workpiece, and a lot of researchers have been attracted to study it. However, as laser energy is too high, the size of molten pool is too small and molten pool contains complex physical phenomenon such as convection of liquid metal, phase change of micro structure and heat conduction. So it is difficult in getting information of molten pool by experimental methods. Then, more and more scholars home and abroad adopt the numerical calculation to simulate laser cladding. In this thesis, Computation Fluid Dynamic(CFD) is used to simulate and analyze the flow field and temperature field of molten pool.In this thesis, pre-processing software of FLUENT is used to establish a two-dimensional model of laser cladding. In order to optimize the two-dimensional model, User-Defined Function is used to add the heat source model and gas-powder flow model and set the initial conditions. Calculating laser cladding by the model includes7kinds of technological parameters with different powder feed rate or scanning speed.By calculation and analysis, it has been found that at the very beginning of laser cladding, molten pool is in a dynamic process of growth. After a certain stage, molten pool is in the quasi-steady-state and the molten pool expands slowly. With the increase of powder feed rate, the molten pool width decreases, the dilution rate decreases, the highest temperature reduces and the largest convection velocity decreases. With the increase of scanning speed, the molten pool width decreases, the dilution rate decreases, the highest temperature reduces, the molten pool temperature gradient rises a little, the largest convection velocity increases.The laser cladding experiments of7kinds of technological parameters mentioned above are carried out by using semiconductor lasers, the coaxial powder feed system and molten pool detection system. The experiments results which agrees with the simulation results are within the range of allowed error. It shows that the model established in this paper is very reliable.