Research On The Preparation, Microstructure Evolution And Performance Of Laser Cladding Layer Based On Amorphous Composite Powder

Due to their high hardness,high strength,corrosion resistance,wear resistance,biocompatibility and soft magnetism,amorphous alloys have an extensive application prospect in the fields of national defense,marine,biomedicine and electronic information.In particular,the appearance of amorphous matrix composites not only solved the problem of brittleness of amorphous alloys at room temperature,but also expanded the application of amorphous alloys in the field of composites.However,the development of amorphous alloys is limited because they cannot be used as structural materials of large size.Based on the development and application of amorphous matrix composites,the amorphous matrix composites were prepared by the combination of mechanical alloying and laser cladding.The forming mechanism of amorphous composite powder,the structural evolution of composite coating and its magnetic or corrosion resistance properties were emphatically studied.The main results were as follows:Nanocrystalline/amorphous and fully amorphous Fe50Ti50 alloys were prepared by mechanical alloying.The results showed that the microstructure of Fe50Ti50 alloy was composed of nanocrystalline a-Fe and intermetallic compound TiFe when the milling time increased from 0 h to 20 h.When the milling time increased to 60 h,all crystal phases disappear,a completely amorphous Fe50Ti50 alloy was formed.After milling for 100 h,the amorphous alloy was crystallized and formed the nanocrystalline/amorphous Fe50Ti50 alloy again.Additionally,with the increase of milling time,the saturation magnetization strength gradually decreased,the coercivity first increased to the maximum value of?143.1 Oe(15 h),and then decreased to?8.2 Oe(100 h)of Fe50Ti50 alloy.The Fe50Ti50 alloys exhibited excellent soft magnetism or paramagnetism.The results showed that the grains size of the nanocrystalline TiFe decreased and the solubility of Ti and Cu in the a-Fe was increased.This was mainly due to a large number of defects(dislocation,twin and hole)in the FeTi alloy during the mechanical alloying process,as well as the smaller atomic radius(0.128 nm)of Cu than that of Fe and Ti.The Fe-Ti based alloys were in situ synthesized by laser cladding technique using Fe-Ti based amorphous powder as cladding material.The coating is composed of a large number of small TiO,eutectic ?-Fe/TiFe2 and micro TiO2 particles after the addition of Cu.The surface modification of laser cladding Fe based amorphous composite coating was carried out by using laser remelting technology.The content of amorphous phase increased,and Fe2B phase and Fe3Mo phase changed to FeB and Fe9.7Mo0.3 phase.In the coating,a small amount of ?-Fe(Fe,Cr)and Cr9.1Si0.9 were precipitated.The coating has higher corrosion potential Ecoor and lower corrosion current density Icorr,the corrosion resistance was enhanced.Moreover,the maximum microhardness was up to 954 HV,and the average microhardness was about 4.3 times of the base material and about 1.13 times of the cladding layer before remelting.