Study On Preparation Technology And Temperature Field Simulation Of Laser Cladding Fe Based Amorphous Alloy Coating

Fe-based amorphous alloy has a unique long-range disordered lattice structure,exhibits high hardness and excellent wear resistance and corrosion resistance,and is widely used in industry as a key component for aerospace,important structural parts for coal mining,and ships to improve the service performance during the manufacturing process of alloy power parts and various parts.As a new material surface treatment and efficient preparation technology,laser cladding has wide application prospects in aerospace,vehicle manufacturing,energy and other fields.In this paper,Fe-based amorphous coatings were successfully prepared by laser cladding techniques at conventional and ultra-high line speeds.The process analysis,microstructure analysis and phase composition analysis of the coatings were also performed.Different lines were also calculated.The amorphous content of the coating at speed.Finally,the change law of the characteristic temperature parameters of the molten pool under different processes i s analyzed by means of numerical simulation,and the formation principle of the coating structure is analyzed in conjunction with the calculation results of the temperature field.In this paper,the thermal difference analysis was first used to verify the amorphous forming ability of the Fe Cr Mo BC powder used in the experiment.The glass transition temperature of the Fe-based amorphous powder was about 622?,the crystallization temperature was about 647?,and the width of the supercooled liquid region About 25?.Combined with Kissinger formula,the crystallization activation energy of amorphous materials is calculated to be about 218.7KJ/mol.Under the conventional process,the thickness,width,dilution rate and other macro characteristics of the coating increase with the increase of laser power.Excessive dilution rate will cause the amorphous forming ability of the molten pool component GFA to decrease,and the coating cannot maintain amorphous state.After optimization,the cross-sectional structure of the single-layer coating under the conventional process can be divided into two parts,which are plane crystals and dendrites near the fusion line,with a thickness of about 50 ?m and an amorphous structure with a large area above.The multi-lap coating is an amorphous-crystallized phase composite coating.The root structure of the remelting zone is a dendrite structure with a thickness of 10 ?m,and the rest of the crystals also appear to varying degrees.The main crystallization phase includes the solid solu tion phase of Fe and the Fe23B6 phase,and the amorphous content of the coating is less than 30%.The thickness and dilution rate of the coating under the ultra-high-speed process are much lower than that of the conventional process,and the thickness of the dendritic band near the fusion line of the coating is only 5 ?m.The multiple lap coatings are amorphous-crystallized phase composite coatings.The thickness of the dendritic zone at the fusion line is about 2 ?m,and partial crystallization occurs under the fusion line.The main phase is the solid solution phase of Fe,including ?Fe,Cr),(Fe,Mo),etc.The amorphous content of the coating is all over 75%.The average hardness of the coating under the conventional and ultra-high-speed processes exceeds 1200 HV,which is 5 times that of the substrate.Within a certain range,the dispersion of the nanocrystals produced by partial crystallization of the coating strengthens,which improves the strength of the coating to a certain extent.The simulation results of the temperature field of the coating under the conventional and ultra-high-speed processes show that the temperature cycle curve of each node along the thickness direction of the molten pool center line is consistent,showing that the temperature gradient increases with the depth direction,and the cooling rate increases with the depth direction For increasing and decreasing characteristics,the temperature gradient of the fusion line of the coating under the conventional process is 52.1×105K/m,and the cooling rate is 5.9×103K/s,and both characteristic parameters decrease with increasing laser power.Under the ultra-high speed process,the temperature gradient and cooling speed of the coating are more than 10 times that of the conventional cladding.The temperature gradient and cooling speed of the fusion line position are 34.6×106K/m and 7.1×104K/s,respectively.Due to the dilution of the matrix,the local solute composition and the ability of amorphous formation are changed.The element transition a rea at the interface accounts for 16.7% and 6.2% of the total thickness of the coating,respectively.The initial cooling rates of amorphous formation under the two processes are 6.72 × 103 K / s and 10.1 × 104K/s,respectively.