Numerical Simulation Of Laser Cladding Ti6Al4V Titanium Alloy Powder On Inconel 718 Superalloy

Nickel-based superalloy is widely used in the manufacture of parts that need to work in high temperature environment for a long time,such as the blades and nozzles of aeroengines and industrial gas turbines due to its excellent high temperature resistance,oxidation resistance and complex stress resistance.However,due to the high cutting temperature and serious work hardening problems,the manufacturing cost of nickel-based superalloy parts is often relatively high.Once these parts are damaged,it will also bring high replacement costs.With the continuous development of economy and society,and China as a big population,the local aviation industry is growing fast.At the same time,with the continuous development of domestic passenger aircraft projects,the demand for high-temperature alloy parts in native aviation industry is increasing.In the face of the high replacement cost of superalloy parts,how to improve the surface properties are becoming more and more important.As an advanced material surface modification technology,laser cladding is showing great application prospects in aerospace,shipbuilding and other industries due to its characteristics of heat concentration,rapid cooling and rapid heating,and small heat-affected area.At present,the accumulation of processing technology for metal material characteristics is a major bottleneck that limits the large-scale application of laser cladding technology in high-end markets.At present,the heat and mass transfer mechanism in the molten pool in the process of laser cladding has not been completely clarified.Therefore,the transient temperature field,flow field and solute distribution model of laser cladding are established based on the finite element method,and the influence of different process parameters on the above physical fields is simulated.(1)The numerical model of transient temperature field was established and the influence of laser power(2000W,2500 W,3000W),scanning speed(8mm/s,10mm/s,12mm/s)and powder feeding rate(5g/min,7g/min,9g/min)on temperature field was analyzed by single factor experiment.The simulation results show that the heat dissipation speed is the fastest along the normal direction of the solid-liquid interface.The scanning speed and powder feeding rate have no obvious influence on the maximum temperature of the molten pool center.For the fixed point on the substrate: the temperature value of the initial stage of the temperature drop is inversely proportional to the size of the powder feeding rate,after340 ms is proportional to.(2)Considering the Marangoni effect and non-isothermal flow,the transient flow field is simulated based on the temperature field.The results show that the formation of Marangoni convection will be affected when the depth of the molten pool is insufficient due to too small laser power or too large scanning speed.At the fixed point in the molten pool,the flow velocity is positively correlated with the laser power and powder feeding rate,and negatively correlated with the scanning velocity.(3)The solute diffusivity of the multiple alloy system is solved by the mixed average method,and the element transport is simulated based on the flow field combined with the mass transfer equation.The results show that the elements are more concentrated at the edge of the molten pool along with the Marangoni convection in the initial stage of cladding,and then diffused in other directions.With the progress of the cladding process,the elements are deposited more at the tail edge of the molten pool.The variation of scanning speed has a great influence on the distribution of elements in the depth direction of cladding layer.When the scanning speed is 8mm/s,the deposition density of elements in the cladding layer will form obvious regional stratification along the depth direction,and the closer to the surface of the cladding layer,the greater the deposition density of titanium elements from the powder.