Research On Microstructure And Properties Of Magnetic Field Assisted Coatings By Laser Deposition

In recent years,as the foundation of laser material enhancement technology and 3D printing technology,laser deposition technology has been widely concerned,and has gradually developed into a new mainstream surface modification technology.The main advantage of laser deposition is the low cost and high surface modification.It can precisely control the thickness and location of the coating and improve the comprehensive performance of the components.However,due to the fast processing speed,the metallurgical process cannot be fully completed.The laser deposition layer is prone to produce metallurgical defects,such as a large number of pores,uneven tissue or even cracking,which reduces the material properties and the quality of parts.These defects cannot be eliminated by adjusting the process parameters and subsequent heat treatment.In this paper,304 stainless steel is used as the base material of laser deposition,and high power CO2 laser is used as the heat source.Under the conditions of different rotating magnetic fields,the Fe106+ 5% Ni/WC powder is made into coating by using the prepositioned powder to study the effect of magnetic field on laser deposition process.Under the parameters of laser power P=2.5kW and scanning speed v=0.3m/min,the circular spot is converted to a broadband spot of 10×2mm by integral mirror,and the broadband deposition layer around 10 mm is obtained.The results of the study show that:(1)The application of rotating magnetic field to laser deposition process can improve the surface quality and spreading property of iron-based coating,and significantly reduce the cracks and blowholes of iron-based coatings,and reduce the surface waviness and roughness of the coating.The surface quality of the coating increases with the increase of magnetic field strength and speed.(2)In the process of magnetic field assisted laser deposition(Fe106+5%Ni/WC),the grain refinement and the homogenization effect on the microstructure of the coating are promoted.(3)With magnetic field assisted laser deposition,the corrosion resistance and wear resistance of the coating will be enhanced with the increase of magnetic field strength and speed.(4)Under the conditions of this experiment,the optimal parameters is when the magnetic field strength is B=70mT and the magnetic field speed is v=600r/min.Compared with the non-magnetic field coating,the surface roughness is decreased by 37%,the hardness is 825 HV,the increase is 18%,the corrosion resistance is raised by 44%,and the wear resistance is raised by 75%.