The Research Of AISI316of Numerical Simulation In Laser Cladding Forming (LCF)

The temperature field of forming parts of Laser cladding forming（LCF）has a veryimportant influence on the microstructure and stress field, and determines themicrostructure and mechanical properties of the molding directly. But it is very difficult toachieve the accurate real-time measurement and control on the temperature of molten pooland it’s ambient in the use of existing facilities. In this paper, parametric programming ofnumerical simulation is used to get the study and verification of three dimensional transienttemperature field of AISI316metal powder of coaxial powder-feed laser cladding, exploreand predict the solidification organization of laser cladding.This paper divided the process of laser cladding forming into laser melting+powderfeeding, proposed an analytical model of coaxial powder feeding laser cladding and modelof powder particles shielding rate and temperature rising in flight process. The shieldingrate was taken to be about10%; a nearly linear relationship between temperature rising ofAISI316powder particles and laser power was found and the smaller the spot size or theradius of the powder particles were, the higher powder temperature was. This paperproposed and defined the concept of critical power of the temperature rising firstly.It was drawn that the double ellipsoid heat source was the most suitable heat sourcefor laser cladding from the analysis of pool shape, internal convection and temperaturegradient. Studying of numerical simulation of laser melting, single laser cladding and lasercladding forming, characteristics (the pool size, temperature, temperature gradient andtemperature change rate) of the temperature field of AISI316was revealed, and arelationship between process parameters with the characteristics of the temperature fieldwas established, and the conceptual and numerical simulation and theoretical calculation ofthe actual critical scanning speed were proposed. In the open-loop condition, thecomprehensive regulation of laser power, scanning speed and intermittent time hadsignificant effects on the controlling the size of formed parts and obtaining uniformmicrostructure and properties. The analysis of solidification organization of laser claddingverified the correctness of numerical simulation results of his article. The solidification organization of laser cladding of the AISI316shows epitaxial growth and is of dendrite form mostly. The thickness of steering dendrite and the remelting depth are increasing with the increasing of laser power and the decreasing of scanning speed. It is also found that the solidification structure is significantly dependent on the occurring time of the highest cooling rate and on that of KYat the melting point of the cladding or the substrate. It is demonstrated that, if the largest cooling rate is achieved prior to KYat the melting point, the structure is of column-dendrite grain form. Otherwise, it is of the cellular-grain form. When KY is less than80×106℃·s, the structure is of column-dendrite grain form. And when KY is more than100×106℃·s, it is of the cellular-grain form. And when KY is more than190×106℃·s, it is of the crystal-plane form.