Study On Process And Properties Of Fe-Mo-Cr Amorphous Coating Prepared By Laser Selective Melting

Amorphous alloys have attracted much attention due to their superior mechanical,physical and chemical properties compared to traditional crystalline materials,and have shown important application value in aerospace,biomedical,and information technology fields.However,the preparation of amorphous alloys is strictly limited by the Glass Forming Ability(GFA)of the corresponding alloy system.The bulk amorphous alloy prepared by the conventional process has a maximum size of only centimeter,which is largely limited.Amorphous materials are widely used in engineering.The amorphous coating not only has the excellent properties of the amorphous alloy,but also greatly reduces the difficulty in the preparation of the amorphous alloy due to the thinner size.The amorphous coating with excellent properties is prepared on the surface of the substrate,which can not only achieve surface modification.The purpose,but also can play a role in reducing costs,is an effective way to expand the scope of application of amorphous materials.In this paper,a Fe-Mo-Cr amorphous coating was prepared by selective laser melting on the surface of 45 steel and aluminum alloy using HK M250 fiber laser.The metallographic microscope,FEI field emission scanning electron microscope,X-ray diffractometer,thermogravimetry/difference were used.The thermal and thermal analysis instrument,Vickers hardness tester and other instruments analyzed the microstructure and properties of the coating.The effects of laser power,scanning rate and scanning strategy on the macroscopic morphology,microstructure and mechanical properties of Fe-Mo-Cr amorphous coatings were investigated.The amorphous coatings after process optimization were thermally stable.Analysis of microhardness and corrosion resistance gave the following conclusions.(1)When the laser power is less than 350 W or the laser scanning rate is greater than 750mm/s,the continuity of the amorphous coating is not good,and the breakpoint will occur when the single pass is prepared,and the combination with thesubstrate is not tight enough;the laser power is greater than 450 W or the scan rate is less than At 450 mm/s,the surface of the amorphous coating was burned,the surface was uneven,and a small amount of pores were present.(2)Due to the dilution of the substrate element,a transition region is formed between the amorphous coating and the substrate,and dendritic epitaxial growth occurs at the bottom of the amorphous coating,compared to the upper portion of the coating,the bottom crystal of the coating At most,as the thickness of the additive increases,the amorphous component of the amorphous coating increases and the amorphous ratio increases.(3)After the process optimization,the optimal laser process parameters for preparing the amorphous coating are laser power 400 W,scanning rate 650mm/s,and lap joint rate of 30%.The XRD diffraction patterns of amorphous coatings on different substrates under the same laser process conditions show that the introduction of Al in the aluminum substrate forms a new amorphous;the XRD diffraction pattern of the thickness of different amorphous coatings shows that from the bottom of the coating to In the upper part of the coating,the amorphous ratio is increased,and the amorphous ratio is 18.68%,34.56%,and 54.98%,respectively.The coating consists of crystal and amorphous.(4)The surface of amorphous coating has a uniform distribution of elements such as Mo,Cr and Fe,but the Al element is enriched or deficient;in the upper part of the coating,Mo and Cr elements are burnt;in the black corrosion area,Mo appears.Enrichment of elements such as Cr,Al,and O.The elemental composition of the gray region is close to the original amorphous powder component and forms amorphous.(5)The mechanical properties of the amorphous coating are significantly improved compared with the two substrates,the microhardness is above 1200 HV,which is 3 to 4 times that of the iron substrate,and 8 to 12 times that of the aluminum substrate;the corrosion resistance of the amorphous coating It is obviously superior to the substrate,and with the increase of the content of amorphous components,the corrosion resistance is enhanced;as the heating rate increases,the glass transitiontemperature Tg increases,the crystallization starting temperature Tx decreases,and the supercooled liquid region ?T decreases.The thermal stability of the amorphous coating deteriorates.