| Amorphous alloys are favored because of high strength,high hardness,and excellent wear and corrosion resistance,and have become an important research direction in the fields of materials science and condensed matter physics.However,due to poor plastic deformation,the machining property of amorphous alloy is poor,which become the main obstacle for its promotion and application.In contrast,amorphous coatings have received more and more attention in recent years,which have inherited the excellent properties of amorphous alloys and have great engineering application value in the fields of manufacturing and remanufacturing.Fe-based amorphous coatings have low material cost,excellent wear resistance and corrosion resistance,and have become one of the research emphases of high performance amorphous coatings.Fe70-xNixSi7.5B17.5Nb5(x=0,5,10,15,20,25 at.%),(Fe0.5Ni0.2)70-yCry Si7.5B17.5Nb5(y=3,6,9,12 at.%)and(Fe0.5Ni0.2)61Cr9Coz Si7.5-z B17.5Nb5(z=2,4,6at.%)alloy systems were optimized in this study.The alloy rods with a diameter of 2mm were prepared by the copper mold suction casting.The effects of Ni,Cr and Co elements on the thermal stability,mechanical properties and corrosion resistance of the alloy were explored.The(Fe0.5Ni0.2)61Cr9Co6Si1.5B17.5Nb5 amorphous alloy composition with excellent comprehensive properties was selected,and Fe-based amorphous powders were prepared by high-pressure gas atomization.Fe-based amorphous coating was fabricated by(High velocity oxy-fuel)HVOF.X-ray diffractometer,scanning electron microscope,simultaneous thermal analyzer,mechanics testing machine,electrochemical workstation and wear test machine were used to analyze the microstructure,mechanical properties,corrosion properties and wear properties of the bulk amorphous alloy,amorphous powders,and amorphous coatings.The conclusions are as follows.(1)The results show that the 2 mm alloy rods of Fe70-xNixSi7.5B17.5Nb5(x=0,5,10,15,20 at.%)and(Fe0.5Ni0.2)61Cr9Co6Si1.5B17.5Nb5 prepared by the copper mold suction casting method are totally amorphous,indicating that the addition of Ni and Co elements are beneficial to improve the thermal stability of amorphous alloys.The(Fe0.5Ni0.2)61Cr9Co6Si1.5B17.5Nb5 amorphous alloy has the largest compressive strength(?max)and compressive plastic strain(?p),which are 4110 MPa and 1.2%respectively.The alloy has the lowest corrosion current density(Icorr)in the artificial seawater solution,which is 1.149×10-8 A·cm-2.The passive film on the surface of the alloy contains four elements:Cr,Co,Si and O.The amorphous alloy(Fe0.5Ni0.2)61Cr9Co6Si1.5B17.5Nb5 has excellent comprehensive properties.(2)The(Fe0.5Ni0.2)61Cr9Co6Si1.5B17.5Nb5 alloy powder with a particle size of18?48?m prepared by high-pressure gas atomization method is amorphous.Amorphous coatings are fabricated on the weld surface of A32 hull steel and A32 hull steel by HVOF.The cross-section coating is uniform and compact with no defects such as microcracks,and the average microhardness is 653.4 HV0.2.Both the coatings and the powders have good thermal stability.When the applied load is 10 N,and the sliding speed is 25 mm·s-1,the coefficient of friction of coating is about 0.4,and the wear rate is 4.5×10-5 mm3·N-1m-1.With the increase of the applied load,the width of the coatings wears scar increases,and the wear mechanism is mainly oxidative wear,accompanied by delamination wear.Compared with the A32 hull steel,the amorphous coatings show low Icorr(6.378×10-7,8.362×10-7 A·cm-2 and 9.286×10-7 A·cm-2)in artificial seawater,20 wt.%H2SO4 and 40 wt.%H2SO4 solutions.The Cr-rich passive film is formed on the surface of the coatings,and the Cr content of the passive film is higher in the H2SO4solution.It is indicated that the coatings have good corrosion resistance.(3)Amorphous coatings are heat-treated at 440,460?and 480?for 20,40 min and 60 min respectively.With the increase of heat-treated temperature and time,the wear resistance and corrosion resistance of the coatings have been improved.The wear mechanism is still oxidative wear and delamination wear,but the degree of wear is less than that of the untreated original amorphous coatings.When the amorphous coating is heat-treated at 480?for 1110 min,the coating is crystallized to form Fe Ni3nanocrystalline phase,and the wear rate and Icorr of the coating are 1.6×10-5 mm3·N-1m-1 and 4.591×10-8 A·cm-2,which are less than that of the untreated original amorphous coatings.It shows that the wear property and corrosion property of the amorphous coating are improved after heat-treated at 480?for 1110 min. |
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