Numerical Analysis Of Microstructure Evolution Of Laser Cladding Inconel 625 Alloy

With the continuous progress of science and technology,traditional steel materials had been difficult to meet the needs in practical applications.The emergence of laser cladding technology provides a new way to solve this problem.As a new material surface modification process,laser cladding technology can effectively improve the surface properties of the material and prolong the service life of the material.However,the cladding layer has the characteristics of high temperature,rapidity and complex metallurgy during laser cladding.The complex physical and chemical reactions occur in the forming process of the cladding layer.It was difficult to study it in real time by traditional experimental methods.Therefore,it was of great practical significance to find a new method to study the forming process of the cladding layer.Numerical simulation technology can intuitively reproduce the evolution of temperature field and microstructure in the process of laser cladding,and the research cycle was short,saving resources,had become a new research method.In the present paper,the finite element model and the finite difference model were constructed respectively.The modeling process of the two models,the simulation results of the temperature field,and the difficulty of coupling with the cellular automata model were comprehensively considered.It was decided that in the process of laser cladding inconel 625 alloy,the finite element model was used to simulate the temperature field,and the finite difference model was used to simulate the microstructure evolution.The change of temperature field during single-channel and multi-layer multi-channel cladding was simulated by finite element model.The temperature field was approximately elliptical,and the heat in the cladding area was highly concentrated.In multi-channel laser cladding,the former cladding process will have a preheating effect on the subsequent cladding process.On this basis,the change law of thermal cycle curve of different nodes on the sample was analyzed.The distribution of temperature field under different cladding process parameters was studied.The cladding temperature was proportional to laser power and inversely proportional to laser scanning speed.And the verification test was carried out for the simulated temperature field results.The simulated cladding profile and size were basically consistent with the experimental results.Based on the finite difference model,a cellular automaton-finite difference(CA-FD)model for crystal growth was constructed.By simulating the growth of equiaxed grains and solute segregation in the cladding layer,it was proved that the model can operate normally and has good stability.The CA-FD model was used to simulate the crystal growth process of single and multi-layer multi-channel cladding layers.The simulated crystal nucleation and growth process conformed to the crystal solidification theory.The influence of different parameters on the crystal morphology was revealed.The results showed that with the increase of the number of nucleation substrates and the acceleration of laser scanning speed,the number of crystals in the cladding layer increases and the crystal size decreases.With the increase of laser power,the number of crystals in the cladding layer decreases and the crystal size increases.At the same time,the accuracy of the simulation results was verified,and the simulation results of crystal morphology were highly similar to the experimental results.Based on the crystal growth CA-FD model,the phase transition CA-FD model and three-dimensional crystal growth CA model were constructed.The phase transition and three-dimensional equiaxed crystal growth in the cladding process were simulated.The results showed that the microstructure of the cladding layer was finally composed of y+NbC+Laves three phases.With the increase of undercooling,the crystal growth rate was accelerated,the crystal coarsening occurs,and the number of secondary dendrites increases.With the increase of disturbance amplitude,the number of secondary dendrites increases,and both primary and secondary dendrites were refined.Similarly,the phase transition results were experimentally verified,and the simulated phase transition process was more reasonable.In summary,the laser cladding process of inconel 625 alloy was systematically studied by numerical simulation,the mechanism of temperature field and microstructure evolution in the cladding process was clarified,and the influence of different parameters on the solidification process of the cladding layer was revealed,which provides guidance for the selection of actual cladding process and the regulation of cladding layer microstructure.