| As a high-quality carbon structural steel,45 steel is widely used in mining,metallurgy and other industrial fields due to its high strength and excellent workability.However,45 steel has a low hardness and poor corrosion resistance,which makes 45 steel abrasion and corrosion serious and affects its service life.Using laser cladding technology to prepare a high performance coating on 45 steel can effectively increase the service life of 45 steel.However,there are many problems in the material feeding in the pre-laid laser cladding,such as weak bonding force and difficult control of thickness.In order to solve the above problems and carry out surface modification treatment on 45 steel,this study adopted composite electroplating method to deposit Ni(Co)and iron-based amorphous powder on 45 steel together to prepare a pre-plating layer,and then this precoating underwent laser cladding.The Fe-Ni coating and Fe-Co coating were obtained.The structure and performance of the coating were characterized by XRD,SEM,TEM,nanoindentation,wear resistance analysis,and corrosion resistance analysis.Some conclusions could be drawn:(1)The Ni(Co)and iron-based amorphous powders successfully deposited on the surface of 45 steel by the composite electroplating.Through the interface observation and EDS analysis of the pre-plating layer,the results show that the iron-based amorphous powders were uniformly distributed in the pre-plating layer.The surface of the pre-plating layer was flat,the thickness was controllable,and it was tightly combined with the substrate.The composite electroplating could improve the material filling and delivery links in the laser cladding,and effectively solve the problems of poor flatness and weak bonding force of the pre-laid powder layer.(2)By optimizing the laser cladding process parameters,the optimal process parameters of preparing Fe-Ni coatings were determined as follows:the power of224 W,scanning speed of 4 mm/s.The Fe-Ni coating of the best process was metallurgically combined with 45 steel.The coating was mainly composed of amorphous area on the top,a fine crystalline area in the middle,and a bonding area on the bottom.The amorphous content in the coating was 45.2%,and the crystalline phase was mainly?(Fe,Ni)phase.The hardness of the Fe-Ni coating of the best process was as high as 12.59 GPa.The Fe-Ni coating of the best process had excellent wear resistance,the wear rate is 0.245 mm3/(N·m),and the wear mechanism of the coating was mainly peeling wear and oxidative wear.The Fe-Ni coating of the best process had excellent corrosion resistance.The corrosion current in 3.5 wt%NaCl solution was 0.1366?A·cm-2,and the polarization resistance was75688.12?·cm2.The corrosion mechanism of the coating was mainly the production of Cl-on the corrosion film solution and the forming of Cr-depleted area.(3)By optimizing the process parameters of laser cladding,it was determined that the best process parameters for preparing Fe-Co coatings are power of 238 W and scanning speed of 5 mm/s.The Fe-Co coating was metallurgically combined with 45 steel,and the structure of each area of the coating was small and uniform,and the size was about 1?m.The amorphous content of the coating was 13.3%,and the crystalline phase was mainly Co Fe phase at the top and middle part and Fe3Co phase at the bottom.The hardness of the Fe-Co coating was as high as 11.21 GPa.The Fe Co coating shows excellent wear resistance under the load of 5 N,7.5 N and10 N.The Fe-Co coating of had excellent wear resistance.The Fe-Co coating in the three electrolyte solutions of 0.1 M HCl,3.5 wt%NaCl,and 0.1 M Na OH showed several times the corrosion resistance of the substrate,which is mainly due to the amorphous phase and forming dense passivation film.In this study,two coatings with a certain amorphous content were prepared by a combination of composite electroplating and laser cladding.Both of them had a high hardness,excellent wear resistance and corrosion resistance,which is helpful to the design of high-performance coatings. |
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