Preparation And Properties Of Fe Based Amorphous Coatings By Electrothermal Detonation Spraying

Traditional thermal spray methods for preparing Fe-based amorphous coatings have two drawbacks.First,the cooling speed is relatively slow,resulting in a low amorphous phase fraction of the coating.Second,the improvement in structural defects such as pores and cracks in the coating is not significant.The detonation thermal spray technique utilizes high-pulse current to cause instantaneous discharge in the sprayed material.The sprayed particles are accelerated to speeds of 2000-5000 m/s under the action of shock waves.The cooling rate approaches 10-6 m/s,which is sufficient to suppress the crystallization of molten droplets,resulting in a higher amorphous phase fraction in the coating.The electric detonation thermal spray method for preparing Fe-based amorphous coatings is an effective means to overcome the limitations of traditional preparation methods.This article utilized FeSiBC-based amorphous ribbon as the spray material and applied a continuous electric detonation thermal spray device to spray it onto the surface of a 45#steel substrate.The resulting explosived products form a high-performance and high-bond strength Fe-based amorphous coating under the action of ultra-strong shock waves.This study conducted numerous experiments to explore and determined several typical process parameters.It analyzed the effects of different parameters on the microstructure,phase composition,porosity,amorphous phase fraction,bond strength,microhardness,wear resistance,and corrosion resistance of Fe-based amorphous coatings.Additionally,finite element calculations were employed to simulate and analyze the variations of sprayed particles during electric detonation.Based on the findings,the following conclusions were drawn:(1)Fe-based amorphous coatings prepared by electric detonation thermal spray exhibit uniform elemental distribution without segregation or other phenomena.XRD and TEM morphology images confirm that the coatings possess a typical amorphous structure,and they achieve metallurgical bonding with the 45#steel substrate.When the size of the amorphous ribbon is consistent with the energy storage capacitor,the optimal process parameters for electric detonation thermal spray are determined to be an initial charging voltage of 12.5 kV and a spray distance of 26 mm.Under these process parameters,the coating exhibits the lowest surface porosity,minimal defects,lowest roughness,and the highest bond strength with the substrate.The deposition efficiency,calculated by weighing method,is also found to be the highest.(2)Under the action of ultra-strong shock waves,the sprayed particles are refined into nanoparticles.This refinement process significantly increases the microhardness of the Febased amorphous coating,reaching a maximum value of 1008 HV,which is higher than the hardness achieved by other manufacturing methods.The three-point bending experiments demonstrate that the coating exhibits good adhesion with the substrate,without any significant signs of tearing or delamination.Under similar conditions,the optimal process parameters used in this experiment result in the Fe-based amorphous coating with the best bending resistance performance.The results of the friction and wear tests demonstrate that the high hardness and refined nano-scale particles of the Fe-based amorphous coating significantly enhance its wear resistance,surpassing that of the 45#steel substrate.The wear resistance ranking is as follows:12.5 kV coating>15 kV coating>10 kV coating>substrate.The electrochemical corrosion tests reveal that in a 3.5wt.%NaCl solution,the uniformly dense Fe-based amorphous coating exhibits higher corrosion resistance compared to the 45#steel substrate.This is attributed to the absence of traditional metal defects such as grain boundaries and dislocations in the coating,as well as the protective effect of Mo elements and the formation of a passivation film.The Febased amorphous coating significantly enhances the corrosion resistance of the substrate.(3)In this study,a finite element simulation method was employed to establish an axial model from the amorphous ribbon to the substrate in electric detonation thermal spray.By calculating the temperature,velocity,and flow field pressure of the flying particles during the spraying process,it further elucidates that the particle velocity and temperature are most suitable,and the particle distribution is most favorable under the process parameters of an initial voltage of 12.5 kV and a spray distance of 26 mm.These findings indicate that the deposition efficiency of the coating is optimized under these conditions.