Study On Preparation And Properties Of Fe-based Amorphous Coating

The amorphous alloy possesses excellent properties,such as high corrosion resistance and wear resistance,due to the disordered atomic arrangement and the absence of crystal defects,such as grain boundaries and dislocations.However,its poor glass forming ability and low tensile ductility will limit the application of amorphous materials as corrosion and wear resistant products.Fortunately,the preparation of amorphous coatings is an effective strategy to show its superiority,especially Fe-based amorphous coatings with higher glass forming ability and lower cost.In this study,Fe-based amorphous coatings were prepared on 304 stainless steel by electron beam and resistance seam welding technique using Fe_23.8Co_3.8Cr_9.3Mo_4.7C₄₀B_17.8Y_0.6 amorphous powders,respectively.The phase composition of the coatings was investigated by X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).The microhardness,corrosion resistance and wear resistance of the coating were analyzed by microhardness tester,nano indenter,electrochemical test equipment and friction and wear tester,respectively.Corrosion and wear resistant coatings were prepared by electron beam cladding technique using WC/Fe-based amorphous mixed powders.The effect of WC content on the microstructure and properties of coatings has been investigated.The wear/corrosion resistant mechanism of coatings and the crystallization mechanism of amorphous powders under electron beam cladding were revealed.The results show that the high energy density of the electron beam causes the dilution of the substrate and most of the WC melting,which changes the original amorphous composition and forms medium-entropy alloy coatings composed of FCC phase.The crack in the coating decreased with the increase of WC content.When the WC content is 30 wt%,the crack disappears.Moreover,the hardness and wear resistance of the coating increased with the increase of WC content.It was found that the coating with 30 wt%WC exhibited the most excellent wear resistance,and the wear rate is 4.42×10-6 mm³/N·m,which is2 times higher than that of the substrate.The wear mechanism of the coating gradually changed from adhesive wear to abrasive wear.The corrosion resistance of all coatings was superior to that of 304 stainless steel,and the coating with 10 wt%WC has the excellent corrosion resistance.Fe-based amorphous coatings were successfully fabricated by resistance seam welding.The microstructure,microhardness,wear and corrosion resistance of the coatings under different welding current were systematically studied.Moreover,coating formation and crystallization mechanism were characterized by welding temperature and microstructure variation of powders at different welding current.The results show that coatings consisted of amorphous phase and crystalline phases of M₂₃C₆,Fe₃C and?-Fe.The dense amorphous coating was fabricated at about 750 K in welding current of 24 A and was seriously crystallized at 990 K in 30 A.As the welding current increased,the amorphous rate in the coating decreased,resulting in a decrease in the hardness,wear resistance and corrosion resistance of the coating.The optimal hardness and wear rate of the coating reached 1280 Hv and 2.71×10^-6mm³/N·m,respectively,which exhibited better performance compared with the amorphous coating fabricated by the traditional methods.In 3.5 wt.%Na Cl solution,the corrosion resistance of all coatings was superior to that of the substrate,and corrosion occurred in the crystallization regions.