| The applicability of Fe-based amorphous coating in special environments such as wear,corrosion and radiation resistance has a very promising future.The superior properties of Fe-based amorphous coating are mainly reflected by the microstructure of amorphous coating.In order to prepare high-performance Fe-based amorphous coatings,this paper attempts to simulate the combustion flame flow of the High Velocity Oxy-Fuel(HVOF)thermal spray and the flight state of the powder to understand and improve the process parameters of the amorphous coating low porosity.Understand in-depth the spraying process factors on the structure and properties of the coating mechanism to further improve the microstructure properties of the amorphous coating.This paper starts with the method of simulation.The material transport reaction model of ANSYS Fluent software is used to simulate the combustion process of supersonic flame.Realizable k-? turbulence model is used to simulate the turbulence.The eddy dissipation model simulates the reaction speed of turbulent-chemical reaction.The discrete phase model calculates the Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 amorphous particles in-flight behaviors.The changes of pressure,velocity,temperature,Mach number and composition in the gaseous flow field were analyzed.Set the different oxygen-combustion flow and the proportion of the two process parameters on the flame flow changes.Study different particle trajectory,dwelling time and temperature information such as flight states,speed changes by adding varying determine particle size.And according to the simulated optimized process parameters,the amorphous coating with different particle size powders was sprayed to test the degree of oxidation and porosity of the amorphous coating by comparing with the discrete phase simulation results.The simulation results show that the pressure in the combustion chamber is very close to the actual pressure,reaching 8.5 atm.The highest temperature of the simulated spray was 3110 K,the maximum temperature at the spray gun outlet reached 2130 m/s,and the simulation predicted that there were 6 Mach cone at the exit.Simulated prediction that the turbulence intensity at the inlet is too large or too small to simulate the combustion.The turbulence intensity inlet of 10%?20%is chosen as the most suitable oxygen-fuel feeding pressure for simulating the flame flow of the gun.Finding that the flame characteristics and accelerated of the powder by 3.0 oxygen-fuel ratio flame is excellent.The pressure in the combustion chamber increases linearly with the increase of oxygen-fuel flow.Flow velocity at the gun exit increase with the total oxygen-fuel flow rising.The larger diameter particle have the longer flight path in the barrel and the longer the residence time.Discrete Phase Model prediction of around 30 ?m particle as-sprayed amorphous coating is best.,which the porosity and oxidation degree is the lowest.Three kinds of amorphous coatings were sprayed for varying sizes of 15?25 ?m,25?35 ?m and 35?45 ?m.It was found that the porosity of the sprayed amorphous coating was the lowest when the powder size was 25?35 ?m.As the particle size of the sprayed powder increases,the sprayed amorphous coating has a lower degree of oxidation.The corrosion resistance of sprayed amorphous coating with particle size of 25?35 ?m performance best in salt spray experiment,which is in line with the selection of spray particles in the simulation of discrete phase. |
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