Numerical Simulation And Test Characterization Of Nickel Alloy Laser Molten Pool Heat Flow Coupling

Laser cladding technology can realize the broken surface repair and material surface modification by forming an alloy layer with the characteristics of wear resistance,corrosion resistance and high temperature resistance,and so on,thus solving the problems faced in heavy equipment manufacturing field that the parts appearing uneven wear,galvanic corrosion,fatigue fracture and other different forms of damage in harsh conditions of longterm service,but the laser process parameters can significantly affect the quality of the cladding layer,it is easy to raise defects like cracks,porosity,powder inclusions,and so on,also since the laser molten pool is highly transient in nature,existing instrumentation is difficult to accurately inspect the laser cladding process in real time,with that,the following studies were conducted:(1)The corresponding theoretical analysis was carried out for different physical fields such as temperature field,stress field and flow field,the mathematical model of laser molten pool heat flow coupling was constructed by setting basic assumptions,constructing control equations and establishing boundary conditions,etc,the heat source model equation was constructed and material properties were identified based on the actual laser cladding process,and the finite element method and the finite volume method were respectively adopted to construct the geometric model of nickel alloy laser cladding temperature and stress field and the geometric model of nickel alloy laser molten pool flow field,on this basis,the control variable method was adopted to set the process parameter combination of laser molten pool heat flow coupling numerical simulation.(2)ANSYS Workbench software was adopted to perform the laser cladding temperature field numerical simulation,revealing the influence mechanism on the temperature field of process parameters such as the temperature field dynamic evolution law,the molten pool internal temperature field change characteristics and laser power,scanning speed and beam diameter,etc,based on this,the laser cladding stress field numerical simulation was performed by sequential coupling method,revealing the influence mechanism on the residual stress distribution and molded part deformation of process parameters such as the stress field dynamic evolution law,equivalent force and residual stress distribution characteristics and laser power,scanning speed and beam diameter,etc.(3)Flow-3D software was adopted to perform the laser molten pool flow field numerical simulation,fully considered the influence of melt flow inside the molten pool and Marangoni effect,revealing the regulation mechanism on the melt flow and molten pool morphology of process parameters such as the molten pool flow field dynamic evolution mechanism,molten pool flow field distribution characteristics and laser power,scanning speed and beam diameter,etc.(4)Based on the numerical simulation results of nickel alloy laser molten pool heat flow coupling,the indicators of molten pool temperature,residual stress,dilution rate and cladding layer defects were adopted to optimize the selection of process parameter combinations,based on this,numerical simulation was used to refine the filtration,so as to determine the characterization process parameter combinations of the nickel alloy laser cladding test.The nickel alloy laser cladding coat was prepared and the nickel alloy laser cladding tests such as macroscopic morphological analysis,physical phase analysis,microscopic morphological analysis and micro-hardness analysis were conducted,thus characterized the cladding quality of nickel alloy cladding and verified the effect of numerical simulation,and in accordance with the indicators of microscopic morphology,dilution rate,micro-hardness,etc,specified the best process parameters combination of laser power 1 400 W,scanning speed 10 mm/s,beam diameter 3 mm.The results of the studies fully reveal the laser molten pool heat flow coupling characteristics,the influence mechanism on the quality of the molten layer of process parameters such as laser power,scanning speed and beam diameter was clarified,and also provide a reference method for the selection of the optimal process parameter combination for laser cladding.